None of the three:
Brutal Legend is almost like a joke - I'm not sure whether it is serious or not. On one hand, it has a pretty decent lineup of metal. On the other hand, it has Jack Black and overrated Tim Schafer gameplay. I don't want to pay money for what turns out to be a troll. Fortunately, it will tank and I might snag a $10 clearance copy (wedged in between copies of Madden NFL 08 and Lair) in a few months.
Bayonetta - I saw that .gif of that zoom-in on her crotch. Sorry, I don't like to play games that ritually embarrass the people that play them. Plus Junpei is going apeshit over the game, which probably steered me away from the game more than anything.
Modern Warfare 2 - I'd get this but by the time I'd go online, there'd be dudes clocking in hundreds of hours, making quick work of me whenever I'm in a multiplayer match.
Edit: I voted MW2 but MW2 >= Bayonetta >>>>>>>>>>>>>>>>>>> Yet Another Tim Schafer Failfest