Here we go.
PS3 all the way. Okay, I'll admit that the 360 and Wii blew the PS3 out of the water 2006 and 2007, but if you haven't noticed, 2008 is now. Here's what the 360 has coming this year that has been getting attention (Correct me as I will likely make a mistake or two): Ninja Gaiden 2 (most people don't care), Fable 2 (pretty cool), Gears of War 2 (Best title for the 360 this year IMO), and maybe Halo Wars. It seems to me that the 360 blew it's load last year, since all the best titles are already out there and becoming older day by day, like Halo 3, Mass Effect, Bioshock, etc.
For the Wii: Every one of my friends who have a Wii have the same story. They loved it at first, but now it is boring and they only play PS3/360. This year the Wii has Brawl, Wii Fit, Mario Kart, uh, I think that is it. I wish you could rent consoles, because this is the one I would rent rather than buy.
PS3: I bought the PS3 late last year knowing good and well how much better the 360 was. But since I don't care about that anymore and the best PS3 titles are just around the corner, I am glad I went this route. As for Games, I don't want to list them all here so please see
this list for all of them. But big names include Killzone 2, Metal Gear Solid 4, Final Fantasy 13, Resistance 2, Haze, Little Big Planet, and a bunch more.
More on the PS3: Free online play. Xbox Live is better today, but this will be answered in Home. Also, if you get a 360, have fun having a hi definition disk player. Oh wait... there isn't one. And have fun having WiFi... oh wait, that costs almost 100$. Not to mention Home is coming out, which will include countless cool things like an Achievements clone, entire online community like second life, and movie/music sharing up the wazzoo. I'll add more stuff as people quote me and complain how biased I am (I'm not, I like the 360 and would have bought one without a doubt if today were May 1st one year ago.