I don't like Bethesda at all, I tried Morrowind and Oblivion, both were incredibly boring to me. I played Fallout 3 a couple years ago and it was fun, but I don't think I'd replay it.
I just finished playing Final Fantasy 13 and Dragon Age 2 this month. Dragon Age is a good series, but I don't like Mass Effect as much for Bioware. Still, had a lot of fun with them. Baulder's Gate was very fun back in the day. Kotor I never really got into, but for whatever reason I do remember Jade Empire some, not bad.
Square Enix, I've enjoyed the recent games, loved the older and middle-aged ones (FF6, FF10, etc) Stories are fun, music is great, love the battles, aesthetics are always lovely, they just make some good games. FF Tactics and Kingdom Hearts are also a lot of fun. I've never liked Dragon Quest though, maybe it's the art style or the spell names, I dunno, just not a fan. Chrono Trigger more than makes up for it though, love it.
It's really close between Bioware and Square Enix. Square has probably given me more games that I loved, and I'm more familiar with them, so they get the vote. Bethesda was way behind though, only game I played of theirs that I liked was Fallout 3 and it wasn't the bee's knees.