I bought 3 games this year. Sim City, Rome 2 and BF4. All on release.
Worst = Rome 2 - The performance of it is just so bad, Crossfire broken, the games battles which are half the game are not enjoyable because of this, plus the fact that I had only played Shogun 2 for a bit and was able to destroy the AI on the hardest difficulty in battles from the get go. Just not worth playing.
Disappointing = BF4 - BC2 on 360 got me into BF (Although I had played on spells of LAN BF2/DC years ago but not in any serious form), bought BF3 on 360 and decided needed to play it properley so built a PC, bought BF3, great fun, not perfect and the maps especially were very inconsistent so tended to just play Caspian, Firestorm, Kharg and some Karkland ones. Then BF4, which offers terrible performance for me, completely inconsistent hit reg and each round tends to be a game of guess which bug will affect me this time. Map design goes from genuinely great to who was smoking what when they thought of that, again probably down to the insane number of game modes that no-one plays needing to be catered for. I still play it as its the only FPS that offers what I want in terms of experience but only rarely now so - biggest disppointment.