1. Nintendo EAD
2. Naughty Dog
3. Media Molecule
4. Retro Studios
5. Atlus
(Capcom and Monolith Soft are honorable mentions)

monolith soft
nintendo ead
wayforward
retro
ubisoft

I don't have a list, but my #1 is Nintendo EAD.

From Software, Atlus, NIS, Sucker Punch, tri-Ace.

My top 7 (not in any particular order)
rockstar
Naughty dog
valve
guerrilla.
kojima
from software 

There's too many can't do a top 5.

5. Bungie - Make fun, polished games that have set the standard in their respective genre. Looking forward to Destiny. 
4. Bioware - Jade Empire & Mass Effect series. Do the whole branching storyline thing better than anyone. 
3. Valve - Everything i've played from them has been exceptional. Also they support their games for a long-long time. 
2. Naughty Dog - Mostly for their 7th gen games. If you want to try cinematic gaming, this is as good it gets. 
1. Nintendo - Literally everything. Their worst games are better than best from others. 

Wildcard: Blizzard - Excellent developer that has made some of most defining games in the industry. 

1. Santa Monica Studio: Creators of the God Of War series, the most epic piece of fiction I've ever witnessed.

2. Rockstar North: Creators of the most recognisable franchise in gaming GTA. The franchise is a hallmark of the most popular genre in the world of gaming.

3. Kojima Productions: Creators of Metal Gear Solid series. The games are well-written and enjoyable. The atmosphere is intense and the environments are well-designed. The characters are great too.

4. Ready At Dawn: Creators of the PSP God Of War games and Daxter and the Wii port of Okami. The games wre fantastic in every sense and its surprising how well they translated these franchises to the handheld. In some ways they are superior to the PS2 games.

5. Bethesda Softworks: Creators of The Elder Scrolls series and Fallout 3. These are some of the most ambitious open-world WRPGs ever created till date.

I think these developers have all helped to revolutionize gaming. They are the creators of some of my favourite franchises.

Old SEGA - Everything until the Dreamcast/PS2/Xbox/GC era.
Old Squaresoft - Everything until the end of the PSOne era.
Old Game Arts - Lunar and Grandia until they stopped making them or started making bad ones ( the creators left or died)
Old Konami - The original MGS, Silent Hill until the PS2 era.

1. Bethesda - Love TES and Fallout series.
2. Bioware - Love the Mass Effect and Dragon age series (aswell as KOTOR and Jade empire)
2. Atlus - Love the Persona series
4. Capcom - Love the street fighter and most of their fighting games, resident evil, Breath of fire (not 6!), Dino crisis, Onimusha, Ace attourney, even though some of those are dormant atm.

5. Monolith - The Xeno series.

Honorable mention 6. Namco - Tales studio.

FROM Software
Square-Enix
Tri-Ace
Nihon Falcom
Naughty Dog