People will criticise the big games, some just for attention, others because they actually didnt like a game. I found halo 3 boring and a bit rubbish until I went back and played through 2 and then the story of 3 gave the game more meaning for me on my second attempt and I enjoyed it a lot more.
ODST is rubbish though, too short, too much playing in the black boring hub level, characters I didnt care about, boring levels, same old enemies... glad I only paid £8 for it - the multiplayer disk made it a worthwhile pruchase all told..