Honestly, I'm not sure where to start but let me start off by saying that this game is possibly one of the worst iterations of the franchise that i've ever played. This iteration is plagued with numerous issues but lets start at the core with gameplay, the most important thing in a game. Under the gameplay segment, there are a lot of topics to address so I'll do my best to split it up into chunks.
Player Movement:
This is probably my biggest issue with fifa 15. In fact, it is the source of most peoples issues with this game. The player movement in this game handicaps players and prevents them from doing what they intended to do. It is clear that this year's iteration of the game attempted to refine the concept of momentum introduced in fifa 14 but unfortunately, it's implementation was downright abysmal. It has become very clear to me that their animation tree has become too complex and this combined with the poor implementation of inertia is the source of the issue. Changing direction drastically reduces your speed which it should to varying extent but it is far to much in this game. It is so bad that it has become impossible to close down a player properly or maneuver through a tight space. As a results, players are able to take the ball from half and run through your whole team to get a shot off. Now, this is as a result of what i discussed above and the ai which i will touch on in a separate segment. I appreciate their desire to push the game in the direction of realism but doing so should not affect a player's ability to control his/her players.
AI:
Honestly, this game is a prime example of EA's development philosophy which is mile wide but inch deep. I will break this down into smaller segments because there is a lot to complain about.
Goalkeeper AI:
As you all know, this year has brought to existence goalkeepers that are worse than those in previous iterations of pes. These keepers are horrible. Firstly, the frequency at which they get beat at their near post is simply unacceptable. In fact, shooting to their near post with semi manual shooting leads to a 100% goal. The lack of individuality is also evident as all goalkeepers in this game regardless of rating play the same. They all fall for the same tricks. Goalkeepers like Casillas love to stay on their line on corner kicks yet in the game, he comes out to challenge for the ball and wins it almost all the time. Goalkeepers like Neuer and Valdes play like a sweeper but in the game, they just stay in their 6 yard box. Again, this is just another example of the mile wide inch deep approach taken by ea. These are just some of the many issues with the goalkeepers in this game. In fact, they are so bad that EA had to nerf it's excellent shooting system from fifa 14 to compensate for the poor keepers.
Defensive AI:
This is by far the biggest AI related issue with this game. The poor defensive ai is the reason people can run right through your defense like Messi while using Sergio Ramos. What is the problem with it you ask? They are static. It's as simple as that. You can only control one player at once yet the AI does not account for that. When a player is coming at full speed towards a defender, the proper thing to do is begin to back off at a speed which allows you to contain the oncoming player or else he will blow by you. Instead of doing this, the ai just remains static waiting for you to switch over to the closest player. Its the desire to focus on the one on one battles but unfortunately, soccer is a team sport. Losing a one on one battle doesn't necessarily lead to a goal. It a sport that focuses on operating as a unit yet the ai isn't programmed to account for this. If the ai was programmed to defend properly, then the game would be a lot better. I almost forgot to mention the catch up bug and physicality cheat on legendary. Under no circumstance should Per Mertesacker be able to catch up with Gareth Bale. The Ai also relies on several cheats in legendary mode including the 180 100% pass to make the game artifically difficult. This is all because they haven't programmed the defensive AI to act as a unit. They need to be active instead of static.
Offensive AI:
Honestly, they really only need to improve the type of runs being made. Its nice to see angular runs but curved runs should be included as well. There needs to be more variety in the type of runs being made and I should not have to press L1 to tell a player to make a run. That needs to be removed from the game complete. In real life, you don't tell your striker or wingers to make runs. They do it based on the situation and the amount of energy they have left. This concept of pressing L1 to make a run only goes to show how much of a back seat the ai has taken in the last console generation. The constant focus on graphics(I will touch on this later) has left us with yawn worthy ai.
There are a lot of improvements to be made in this department and I surely haven't mentioned all the issues.
Player & Team Individuality:
Again the common theme here is the mile wide inch deep approach. It's one thing to nail their looks but its another to nail their movement and behavior. Now there are thousands of players in this game but you need to begin somewhere. In every league and every team, there are maybe one or two players who stand out in the way they behave and the way they move. The way ronaldinho runs and plays is different to the way ronaldo runs and plays. In fifa 15 however, they may as well be the same person. When they are controlled by the AI, they just play like all the other players in the game. When I play against Ronaldinho, I want to see him use skill moves to beat players in a one on one battle. I expect him to attempt no look passes and to have superior passing vision. I expect his set pieces to be unique to him. The same goes for ronaldo. When I play against Juventus, I expect Pirlo to be the focal point for their attack. I expect him to run the midfield and distribute the ball like no one else. The same goes for players like Xavi as well. These are some of the things EA needs to focus on to really improve the game. Their shallow additions are reall becoming less and less note worthy always failing to justify the new iterations of the game.
Presentation & Graphics
Graphics:
The transition to the new generation of consoles has been extremely disappointing. Instead of attempting to push towards photo realistic graphics, EA has instead chosen to double down on their pixar look for the game. Everything about the game's graphics is disappointing including the grass. From the lack of AA to poor jersey models, player skin tones, crowd model skin tones, crowd model clothing attire, color of the grass, etc. The whole game just looks like a cartoon. I know that you can't start from scratch every generation and you need to build ontop of what you have but fifa has not improved at all. It just looks like a ps3 game with more effects to me. This is the difference between last gen player models and next gen player models in nba 2k14:
This is the difference between Fifa 14 on the ps3 and ps4:
Here is pes 2015 vs fifa 15 and don't forget, Konami has far less resources than EA:
Fifa hasn't made this jump yet and I'm still waiting for a next gen looking game.
Presentation:
Again the common theme is mile wide inch deep approach. They have made the game look like a tv broadcast but they haven't still addressed some important issues. Crowd chants are still static. It needs to be dynamic. It needs to be a push and pull mechanic. At the Barca vs PSG game in Camp Nou, when the PSG fans started chanting, the Barca fans responded drowning them out. It's a us vs them mentality. When Atletico Madrid fans where chanting in the Bernabau, Real Madrid fans responded by whistling to drown them out and then they started chanting. It takes a lot to capture the atmosphere of a game but if they can capture the emotion, then it makes the game special. Fans tend to target opposition players depending on how they played and in fifa they need to implement this. If you are playing against a rival, then the game needs to remember(career mode) what happened in previous games and that should dictate how the fans react. If Pepe injured Messi in the last game then everytime he touches the ball, the fans should boo(north america)/whistle(spain). Things like this make the game feel alive. In fact, it is so of putting to be playing a game in spain and hearing the stadium announcer make announcements in english.
These are just some of my many complaints with fifa 15 and the franchise as a whole. They are always chasing the next back of the box feature instead of attempting to emulate the sport with it's little intricacies. Honestly, I could write a book titled what is wrong with fifa but no one would read it.