I can usually tell fairly quickly whether I'll like a game or not, but I tend to atleast give it a chance to change my mind. How long that chance is varies from game to game. A shooter or action game which lasts around 10hours, I'll probably give it 2 hours. RPGs on the other hand, which could last more than 30hours, I'll give atleast 5.
Few years back I won a copy of the Unreal Tournament 3 collector's edition, before that I won a copy of Full Spectrum Warrior along with some goodies linked to it. Admittedly I tend not to enter contests unless it takes me less than 1min to do, generally just not worth the effort.
I'm sure it's just those reviewers. Mortal Kombat has been at the top of the sales charts in quite a few online uk retailers. Plus everyone I know who owns it really likes it. The downside is not being able to play online(I own the PS3 version), but that's down to sony, not the game itself.
Indeed, Abyss 3DS this year and Graces f next. I just hope there isn't that much of a difference between the european release date and the american one. I managed to get a preorder in for Graces f at $40(Amazon misspricing ftw), so if europe has to wait longer, then I'll probably keep that and get it from there. Otherwise I'll older it from whichever UK retailer is selling it cheapest so it adds to european sales.