Sucker of the good ol' peer pressure, huh? My situation was kinda similar. They indirectly peer pressured me to get a 360 because so many of my friends were having so much fun, I just got jealous

Wii : Super Smash Brother , Wii Sport 

PS3 : Fallout 3

DS : Mario And Luigi Partner In Time , Mario Party DS

PSP : Patapon

When I got my DS I got

Mario Kart- happy

Mario and Luigi Parnters in Time- happy

Tetris DS- happy

Ridge Racer DS- eh

This is what I got right off the bat that I can recall followed by New Super Mario Bros (Happy) a few months later.

When I got my Wii I got

Wii Sports -happy

Mario Kart Wii -happy

Super Mario Galaxy- happy

Super Paper Mario-happy

Super Smash Bros Brawl-happy

Mario Kart came out as I finally got a Wii

Really no one game got me to buy them. But, it was Nintendos first party games that did, which is what makes me always buy Nintendo consoles. I have since added many games from Nintendo and from 3rd parties to both over the years.

I almost always buy a system based on what 1st party has to offer. I had Sega systems because of Sega I had Sony systems because of Sony too. Only once did a 3rd party game have much influence and that was FF 7, but Crash Bandicoot is what tip the scale for me to get my PS1

I got the Wii and DS because I really liked the Gamecube and GBA, but the games that sealed the deal were The Legend of Zelda: Twilight Princess for the Wii and Pokemon Diamond for the DS.

The PS3 I got as soon as the slim came out.  Thought I'm not sure I would have bought it if it weren't for Enchanted Arms and the knowledge that Final Fantasy XIII, God of War III, and Gran Turismo 5 were coming out for it, the sequels to my favorite games on the PS2.

I should also add that when I get a 3DS it will be once again because of what games Nintendo has to offer

Animal Crossing- I dunno why but i love this game and so does my GF and her daughter

Kid Icarus: Uprising- it has been years since I have got to use Pit in his own world (most wanted atm)

Mario Kart- Ive owned everyone of them and only the GC one let me down some

Paper Mario- always a fun game

PilotWings Resort- could use a good flying game havent had one since N64 PilotWings funny enough

Star Fox 64 3D- not the biggest StarFox fan in the world, but I really loved the SNES/64 ones

Steel Diver- Sounds interesting not sure it will be a buy yet though

Some 3rd party games I am wanting too, but these right here along with hopefully another New Super Mario Bros game is what will make me want it

PS3 - Final Fantasy XIII (Worth It)

360 - The Last Remnant (Worth It)

NDS - I got it for free, twice by trading money in a game.

PSP - Crisis Core (Worth It)

Wii - Got it for free, but I would say not worth it if I had to pay for it.

PC - Final Fantasy XIV (N/A It isn't out yet!)

Wii: Nintedo games, but mainly New Super Mario Bros Wii and the iminent release of Donkey Kong Country Returns.

X360: Rock Band, Sakaguchi games and the fact my best friend had one

DS lite: FF remakes and the fact it played GBA games

PS3: Only got it a week ago my reasoning was
Uncharted 1 & 2
Disgaea 3
Metal Gear Solid 4
Valkyria Chronicles
Little Big Planet 1 & 2
3D Dot Game Heroes

Plus Amazon accidently gave me a $185 refund, so I got it super cheap

i bought a ps3 because it was BC to my ps2 games. I now own a non-BC ps3 and don't really miss BC but if it was the case at the start, I might have opted for a 360 instead. I will never know now.

PS3: Metal Gear Solid 4 and Soul Calibur IV