Most of you here probably knows which developers I like by now, but I'll still list them as a formality:
-By the way, unlike most of my lists, this one actually IS in order from most favorite to least.-
1. Nintendo: The obvious first on my list. You can't go wrong with them, or at least it's highly unlikely that you would. I always favored the Metroid and Zelda series over all else.
2. Square soft: I know it's Squre-Enix now, but I never played most of Enix's games other than Dragon Warrior, and I'm still not a huge fan of it. Anyway, I've always enjoyed the Final Fantasy series.
3. Capcom: They have made some great games, but they also go overboard with all of their sequels. I'm a huge fan of Mega Man, but after Battle Network started, I started to lose interest. Even Mega Man Zero didn't bring any hope back for me, and I can't say ZX improved anything either. So yeah, here's to the old Mega Man games. Phoenix Wright has also become one of my favorite games, but the new and upcoming 4th game doesn't really seem necessary to me.
4. Sega: Mostly for Sonic, really. Although Sonic went downhill faster than even he could run, we always will remember the times when Sonic was a good series. Not to say that Sega hasn't had a lot of other good games, I was just never a Sega person.
5. Konami: Is pretty good.
6. Rare: Had some good games as well.
7. Hudson: Bomberman.
Meh, I can't think of any more.