1. Mass Effect
2. Thief
3. Fallout
They are all equally my favorites Honorary mention is: Splinter Cell (up to Conviction). There are single games I've loved but it'll be off-topic.
Side note: the only reason ES series are not on my list is because I started with Skyrim and didn't have experience with other games in the series.
Only 3?!!! ok out of what's listed below--ElderScrolls, Fallout, Hitman---
RPG's Action/Adventure:
Elder Scrolls,Fallout
Shooters:
Hitman Silent Assasin-Absolution,the entire Battlefield series, Max Payne, Halo 1-3, Splinter Cell, GTA 1-4 +RedDead
Fighting: MK 1-9 + Mk vs DC/Injustice
I have to post again on this one it's a really fun topic! these don't count as series' but they are still excellent classics that everyone should be able to recognize from the 90's
-Goldeneye/Perfect Dark (Obviously N64)
-Conker's Bad Fur Day (N64)
-Red Faction (PS2)
p.s. (So ya'll dont think I only play shooters)- Tony Hawk's Pro Skater 1-2
1:Elder Scrolls(Obviously)
2:Metal Gear Solid(Love the story and the gameplay)
3:Sonic(I grew up with these games)
4:Legend Of Zelda(I grew up with these as well)
5:Mario(Grew up with it)
I have a lot more,but my real favorites would have to be
1:Final Fantasy
2:Legend Of Zelda
3:Sonic
1. Pokemon (DON´T YOU DARE LAUGH AT ME YOU IGNORANT BASTARD!!!)
2. Elder scrolls
3. Battlefield
A little bit of everything. I played every single Pokemon (even some weird ass Japanese ones) so that´s why I put it on the list. My friends and I still play Battlefield almost every week and it is just such a great franchise.