As title implies, I recently installed a Windows partition on a 2020 Macbook Pro and I'm looking to revisit some games that are relatively simple to get into from the mid to late 90s-mid 00's era. Shooters, RPG, Action games mostly.

So far I have:
Enclave
Deus Ex
Divine Divinity
Heretic + Hexen

Added to my cart.

Other GOG (actual old games) that I own from previous times are Nox, Giants Citizen Kabuto, Darktstone, Might and Magic Series, NWN, Rune, Thief 1 and 2, Unreal games, Ultima Underworld games, to give you all a frame of taste.

Thanks in advance!

If you like Descent-type games, do try out Forsaken (Remastered) - it's currently on sale. While technically not old, since it's a remaster, it still is very faithful to the original 1998 game, which I actually enjoyed more than the "Descents".

I will always recommend the classic Fallout games (yes, Tactics included).

That is a whole swath of ranges you are talking about there, covering FPS, RPG, strategy, action, stealth, plus others. You might want to narrow it down. What about games styled like those from the 90s but recent? What about gzdoom mods? Really too broad.
In terms of FPS, shadow warrior game,s and the newer 2013 are great. Blood another. For RPG, dragon age origins. UUnderworld, perhaps legend of grimrock.

https://www.gog.com/game/battlezone_98
https://www.gog.com/game/sacrifice
https://www.gog.com/game/outcast

absolutely, my search is a bit on the overwhelming side, moreso funneled down into what games can actually run on my system before it sounds like an airplane. So, no modern games with a 90s feel UNLESS they have low system requirements I guess. this is what im talking about, thanks!

and thanks to the other posters recommending games off the cuff, that's exactly why I came here to ask :)))

Thought this was an interesting topic idea, my first thoughts for FPS are that you can never go wrong with the original DOOM and DOOM2 games. Great arcade style shooters, all action, little wasted time. For RPG in that era, the Star Wars Knights of the Old Republic games are still among my favorite non-D&D setting RPGs. Choices generally have obvious outcomes, but in some cases they do matter unlike so many of the 'modern' games where any character can do anything at any time, you cannot do everything or play every character in a single KOTOR game. Good luck choosing something, there have been several other great suggestions already.

The Tomb Raider games are still awesome. I can also recommend the Prince of Persia games as well as XIII, Metal Gear Solid and Street Fighter Alpha 2

How about:

Albion (1995)
Tomb Raider 1-3 (1996+)
Outlaws (1997)
Oddworld: Abe's Oddyssee (1997, remade into New and Tasty)
Oddworld: Abe's Exxodus (1998)
Rage of Mages (1998, simple RPG/skirmish RTS mix, admittedly I'm not sure if it still holds up but I liked it)
Rage of Mages II: Necromancer (1999)
Outcast (1999)
Tomb Raider: The Last Revelation + Chronicles (1999/2000)
Revenant (1999, not the greatest game ever but enjoyable enough)
MDK 2 (2000)
Vampire The Masquerade: Redemption (2000)
Throne of Darkness (2001)
Evil Islands (2001, also not the best, but decent)
Gothic (2001)
Gothic 2 (2002)
Arx Fatalis (2002)
Prince of Persia: The Sands of Time (2003)
XIII (2003)
Star Wars: Knights of the Old Republic (2003)
Vampire The Masquerade: Bloodlines (2004)

Arcanum is another great RPG from the original designers of Fallout.

I'm legally required to mention Pajama Sam Vol. 1 ;) but those are adventure games.

Shadow Warrior Classic is free and very fun but you might have to spend a little time getting it to work with a source port.

Blood is the pinnacle of Build shooting
Serious Sams
Postal 2 (only $1)
Carmageddon 1 and 2
SiN Gold
Tomb Raider 1-3 (though if you didn't grow up with those controls, you may find them rough)
Medal of Honor
Zombie Shooters
Flatout 1-2 (racing)
Quake 1
Doom 1
Jedi Academy
Bio Menace (free and fun, but really tough for me; I went ahead and cheated a lot)
Tron 2.0
Crysis

Also, Requiem: Avenging Angels and Red Faction are halfway decent FPS game with some interesting mechanics, though not as good as Heretic, Outlaws or XIII.

oh wow, havent touched prince of persia since the 09 reboot. before that was PoP 3D as my first PC game with a graphics card. Thanks!! I have the Doom games on my Switch, but keyboard doom really is king. KOTOR is a great pick, thank you. And on sale! Blast of nostalgic awesomeness right here, thank you. Some of these I remember seeing the box at the store but had no money to buy as a kid like Revenant.

I have Arx Fatalis and actually just started playing; is the Arx Libertatis port the way to go for a first blind playthrough? I thought the game looked pretty good.

Red Faction was amazing! Never heard of Requiem I don't think. Thanks!

TRON 2.0 is still one of the best FPS games I ever played.

Same goes for SWAT 4.

Diablo is a no brainer, for me it's still the best hack'n'slash ever made.

Unreal is surprisngly great. I have not played it back in the day, only once I got it here and although the graphics sure have aged, the gameplay and atmosphere are still rock solid.

The gameplay of Armed & Dangerous on the other hand isn't exactly fantastic, but it's still one of the funniest games I ever played, and there's just so much humor in both the story and the gameplay (land-shark launcher!) that it's still a blast to play.

Indiana Jones and the Emperor's Tomb - plays something like an early Uncharted before the actual Uncharted, and it's a very solid use of the movie license. The only drawback are some frustrating levels near the end and a lackluster final boss fight. But if you like Indy or just action games like Uncharted and Tomb Raider, it's still quite good.

Judge Dredd: Dredd vs Death - this one is nothing great, but sometimes you may just want to play a simple, solid shooter without any bells and whistles, or overlong complex levels. Just go and shoot and have some fun.

Robin Hood: The Legend of Sherwood - ok, so this maybe doesn't fit the genres mentiond by the OP, but I just can't hel listing one of my personal favorites. It's basically Commandos but in medieval England, with Robin, Little John and all the rest. The graphics are still beautiful in my opinion, it tells the familiar story well, Robin's adventures translate to this kind of stealth/tactical combat hybrid perfectly, you get to run your Sherwood encampment in between missions, and it has the super fun mechanic of actually controlling any characters movements in melee combat with your mouse, making for great duels or epic scenes with holding back whole squads of guards with Little John.