The difference between all the other games and Battlefront II is that the other games hide only cosmetic items in what you purchase. BF2 hides certain abilities that give the player who put money in an advantage over all other players basically making the game not fun unless you pay extra. You can play the game without paying, but expect to die a lot and feel frustrated which is why this game has been getting so much controversy compared to other games.
The developer/publisher (whoever decided this) also locked Darth Vader, Luke Skywalker and most of the other popular characters behind paywalls, so do not expect to play as the main characters of the game until you put in 40+ hours per character. I have the game as I bought it used at Gamestop (as revenue goes only to GS), and it's an okay game. I got through the full story in only 3 and a half hours, so if you are mainly interested in the single player definitely wait till it goes on sale or you can find it used.