http://irrationalgames.com/ - creator of System Shock 2, SWAT4, Bioshock and upcoming Bioshock Infinite.
http://platinumgames.com/ - the people from the former Clover studio deliver games that aren't particulary deep, but great deal of arcadish fun like Mad World and Vanquish.
http://www.sega.com/ - Virtua Fighter, Shenmue, Yakuza, Valkyria Chronicles and so on, they developed a lot of great games over the years. They are probably my favorite publisher of 2010 as well, considering how they released a lot of new IPs that year instead of just playing safe like most publishers do and rely on sequels. SEGA isn't without fault regarding this though, as they milk Sonic like crazy, but meh
http://www.konami.com/ - because of their 2D Castlevania games but especially their Suikoden series. I want a Suikoden VI!
http://www.obsidianent.com/ - for Alpha Protocol and Fallout: New Vegas.
But my favorite game studios of all time are Origin Systems (Wing Commander, Privateer, Bioforge, Crusader), Looking Glass Studios (System Shock & Thief), Ion Storm (Deus Ex) and Troika Games (Bloodlines), and they are all dead now
Especially LGS was super awesome.
There are numerous other studios I hold in high regard because of one game or another, but eh, this list would be too damn long if I wrote them all down
Now, as for studios I dislike...
I hate Valve, because they seem to think they're the best studio ever. Half-Life is fun, but TF2 and L4D are SO overrated in my opinion. They do have an amazing PC games platform though.
I also dislike Blizzard, since I dislike RTS games. I also find WoW overrated.
I kinda agree with those, but I dislike Valve for another reason. I dislike Valve simply because they introduced online DRM for single player games. Even if you buy Half-Life 2 in a store, you still need to go online and activate the game to be able to play the single player part of the game. That's a horrible development, and since then we seen a lot of other companies doing similiar things. But Valve created the snowball and got it running, and for that I despise them.
Lucasarts used to be the greatest developer studio in the world as far as I'm concerned, but then in 1997 they released Star Wars: Masters of Ter?s K?si and since then they continued to go downhill with various poor Star Wars games. Now they are nothing.
Ubisoft haven't managed to release a game that catched my interest since Beyond Good & Evil back in 2003. I was majorly disappointed in the Splinter Cell series as well as the Thief series have much better sneaking mechanics, and also disappointed in that they actionified their two strategic shooter series Rainbow Six and Ghost Recon. Their extreme DRM last year didn't really make me think better of them either.
I'm also rather disappointed at what Square-Enix done lately. All they seem to do is to release remakes of their older FF & DQ games. And their newer games have gone downhill ever since FFX (which I think was rather poor aswell). During the PS1 days they created numerous of new IPs and they were all great fun, like Threads of Fate and so on. Now they just play safe, which is boring. They did release a lot of brilliant games for the SNES and PS1 though and are still worth watching (especially so after buying Eidos) so I don't really dislike them. Just disappointed in the direction their FF series gone and a few other things.