-Nintendo: Lots of amazing games in their repertoire, and they single-handedly revived gaming after the video game crash in the '80s. They're also practically the only big company who still remembers that fun is the most important part in a game, and that games should be games. Probably my favorite video game company, along with...
-Sega: Made a lot of amazing games back before they were forced into being a third-party. Still release some good stuff, though they aren't as big as they used to be, besides Sonic Team's stuff. Their Genesis, Saturn, and Dreamcast stuff is still just amazing and diverse.
-Capcom: Back in the day, they could do no wrong. They've ran into some problems with gamers recently, but I still think they can make (or outsource, hah) some great games.
-Namco: Lots of classic arcade games under their belt, and some great 3D fighters like Tekken and Soulcalibur. Just love them. I could play their games for hours.
-Konami: Castlevania, Contra, Metal Gear, Silent Hill, and a bunch of classic NES, SNES, and Genesis games earned them a spot in my top developers.
-Rare: When they worked with Nintendo, anything they made was basically like playable gold. While I still enjoyed some of their later games, they just aren't the same anymore, but their classic games still hold up great, and will forever be some of my favorites. The Donkey Kong Country series is still up in my favorite platformers of all time, and Perfect Dark is still my favorite first-person shooter. All of their SNES and N64 stuff is just amazing, and damn could they pull off some amazing stuff on those.
-Treasure: I don't think these guys could make a bad game even if they tried. Everything they make is amazing, from incredible 2D games like Gunstar Heroes, Dynamite Headdy, Guardian Heroes, and Mischief Makers, to spectacular 3D games like Radiant Silvergun, Ikaruga, and the Sin and Punishment games, these guys just can't do wrong. Hell, they even made a game starring Ronald McDonald that turned out to be awesome!
-SNK: Amazing back in the '90s. Arcade game heaven. They could do wonders with their spritework, showing that even decades old hardware could kick some ass.
-Ubisoft: Pretty much here solely because of the Rayman series, but damn, what a series it is! One of the platforming greats.