I say get GTA 4, Assassin's creed is a great game but after a while it will get repetitive and boring and will be one of those games that just sits on the shelf. however, i would have to agree with the second post, Oblivion is the best RPG ive ever played
Get Assassin's Creed II it's an awesome game, easy achievements and is better than the original in every way
Bayonetta is basically just Devil May Cry, I haven't even touched that game since the day I bought it. GTA IV is a must have, you won't regret it.
I think you should play it, you will be shocked that it is like DMC (Don't forgot that DMC creators helped with this game) but it has its own originality to it.