In my life? Nintendo by far. Sony wasn't even on the radar until I'd been gaming for around 6 years on the NES and SNES. Even now I enjoy Nintendo games more. That said, I'm currently catching up on the Uncharted series and inFamous (just bought a PS3) and I'm enjoying them both.

First Party, Sony
Third Party, Atlus, then SE. From Software and NISA closely behind.

First party: Sega.

Third party: Capcom.

The list of their IPs I've played is huge and posting it would take forever...

First party - Nintendo:

Mario
The Legend of Zelda
Metroid
Star Fox
F-Zero
Fire Emblem
Super Smash Bros.
Wii Sports
Ice Climber
Duck Hunt
Pokémon (not sure if this one counts)

And the mandatory Mario spin-offs such as Mario 2D/3D, DK, Yoshi, Wario, Mario Kart/Golf/Tennis/Party, Luigi's Mansion.


Third Party - EA:

Battlefield
Dead Space
Mass Effect
Need For Speed
Rock Band
Bunch of sports games on occasion.

1st party  - Nintendo

3rd party - Valve (not by quantity but on how many hours I invested in Valve games)

1st Party: Nintendo (unless we count every separate Windows related program (Word, Power Point, Money etc.) since Windows '95 as its own IP.

3rd Party: Capcom

List how many games you've played within those decades and look at the IP's im not talking about assumptions. I thought I had played EA more than Sony and Square Enix but those ended up being my top two. In my lifetime I ended up playing less Nintendo IP's (not games) than Sony.

If you're having a hard time just make a quick list like I did and tally it.

List your favorite or most known third party IP's (not games) and you'll find out who your real top third party is. I found out mine is Square Enix....money grubbing bastards. LOL

First party- Probably Sony has they seem to just have more franchises. But, i have played a lot of Nintendo's titles too.

Third party- Rockstar- i have played almost everything they every made. Sega- is not far behind, they have made many classics over the years.