In no particular order

I am going with specific developers for my list. So no big publishers under one spot.

• Remedy Games - Both Alan Wake games are in my top 10 favorite games of all time and I was blown away by AW2. I am excited to see what they can do with the Max Payne 1 and 2 remake.
• Playground Games - Forza Horizon from what we know is now the biggest 1st-party game from Xbox Game Studios and the little bit of what we saw of Fable looks fantastic. 
• From Software - I recently started Elden Ring, my first attempt at a Soulslike game, and while I am struggling a bit it is still a lot of fun.
• Rockstar Games - They've only released 1 new every 5+ years lately, but Red Dead Redemption 2 is one of the best games of the last generation and Grand Theft Auto VI looks like it is going to be amazing. 
• ID Software - They popularized first-person shooter genre with Wolfenstein 3D and Doom. The recent Doom games are fantastic. 

Honorable mentions

• Bungie - Halo is my favorite gaming franchise, however, I have no interest in Destiny. So they haven't released a game that has interested me since Halo Reach in 2010.
• Bethesda (Core team lead by Todd Howard) - The Elder Scrolls franchise, Fallout 3 and 4, and Starfield. I enjoyed Starfield, but didn't love it. If Starfield lived up to my full expectations they would have been in my top 5.
• Santa Monica Studio - Only have played God of War (2018) from them on PC and it is easily my favorite game from a first-party PlayStation studio. I'll play Ragnarök once it comes to PC.
• Rare - So many classic games released in the 90s, but haven't released as many games. Though, Sea of Thieves is a great game.
• Capcom Division 1 - Developer of Resident Evil, Mega Man, Devil May Cry, Dead Rising, and more.
• Sonic Team - Genesis / Mega Drive Sonic games are some of my favorite games of all time. 3D Sonic games haven't lived up to those games, though, Generations is good.

There are probably more honorable mentions, but that is what I can think of off the top of my head.

Just to follow up from my original post, I listed my general top 5 studios ever, but there are still 5 studios today that still get me pumped when a new title is released from them.

I'll have to thrown in a few honorable mentions

Fromsoftware
Sony
Capcom
Nintendo
Rocksteady and Konami the batman games are superb and so is the mgs franchise.

I kinda had an idea to make a favorite game company by decade thread but for now I'll just post my picks here. Feel free to steal that idea if anybody wants.

1990s:

1. Konami
2. Square
3. Nintendo
4. Game Freak
5. Valve

90s Konami is underrated, they were killing it back then with Symphony of the Night, MGS, Silent Hill, Suikoden. Square and Nintendo had better singular games in FF7 and OOT though.

2000s:

1. Bandai Namco
2. Blizzard
3. Nintendo
4. Valve
5. Atlus

Nothing beats the golden era of Tales games, arguably the 3 best entries back to back within 5 years. Blizzard was also killing it with Warcraft III and WoW.

2010s:

1. Blizzard
2. Bandai Namco
3. Nintendo
4. CD Projekt Red
5. PlatinumGames

I played everything Blizzard released in the 10s and though it wasn't all perfect it was all pretty damn good. CD Projekt Red might be first if they had released a bit more. Bandai Namco might seem weird up here but don't forget they developed Smash 4 and Ultimate.

2020s:

1. Nintendo
2. Crowbar Collective
3. Omocat
4. Santa Monica Studio
5. Moon Studios

This one's based almost exclusively on individual games, since we're so early in the decade. Crowbar Collective and Omocat are behind Black Mesa and OMORI for those who don't know, both unlikely to release more games if we're being honest.

Overall Nintendo is of course my choice having stayed in the top 3 through every decade.

1. Sega
2. LucasArts
3. Remedy
4. Square (Enix)
5. Origin

Fromsoftware
Larian
Atlus
Obsidian (purely because of fallout nv)
Rockstar

Update - I forgot about rockstar so replaced santa monica with it

Nintendo, then Square Enix, Sega, Namco, Capcom. No particular order for the last four.

For me the "top" 5 would be:

Naughty Dog, From Software, Square Enix, Capcom and Atlus.