I suggest the Wii games. Then get a PS3 Christmas, so then it'd only be a couple months before it's your birthday again in February.

Making the jump to HD isn't a bad idea. More games isn't a bad idea either. With the PS3, you can try demos for free, and even do things like play mini-games on Home and check out the features it has to offer. Metal Gear Solid 4 isn't a bad investment either since it also has online gameplay, which would last you a good while. Another option would be to rent PS3 games if you're short on cash or even borrow them from friends who have PS3's. The choice is up to you. New experience or more games. Love the PS3.

Get the PS3 it's definitely worth it. You got GOW3 coming up FF13 & GT5!!!

Since cash is tight go for the Wii games, espcially the ones with multiplayer they last longer!

If you really have a tight budget just stick to buying the Wii games you want, I would advise you to save up more money for a PS3, although the start cost of a ps3 is not too bad, once you start buying all of the quality games for it, it soon becomes expensive, this month alone I had to chose between WKC(it is not as bad as reviews say) and HR, and next month I have to choose between GOW III, FF XIII, ROF, SO4.
Eventually I will get all the games, but not even I can afford them all, and I already have 16+ PS3 games.