Decided to play some quake II and figured what the hell lets mod it. Currently running Quake II XP, but I've heard there are better hd textures/models out there.
Tempted to do the same with Duke 3d, provided I can figure out which version I need to use as a base for my mods.
Hands down eDuke32 and Megaton Edition.
Unfortunately, you can't legally buy Megaton Edition anymore if you don't already have it. It's very hard to find a physical copy of it.
You can sail the seas to get it, but that's the only way unless you manage to track down a physical copy, which will likely be expensive given how high demand they are.
Atomic Edition is the next best thing. You can buy a physical copy of it on Amazon, and it's pretty cheap that way. Unfortunately, that is the only way to get it. It's the complete main game, minus some of the expansions. The expansions are fun, but none are as good as the main game.
You will need a disk drive to install it, but once you have it in eDuke32 will run the files for you on modern Windows systems.
The only way to legally get Duke 3D digitally currently is to get the shitty World Tour remaster Gearbox released. They discontinued every other version, which is a shitty habit they are developing as of late. They did the same thing to all the Borderlands games.
World Tour does have some new content, another episode I think. It also lacks many of the features of the Megaton Edition, such as being able to turn off Mouse Acceleration, and there are a lot of other issues. It's a crap port with some extra post processing slapped onto it and some "I've got a mortgage" level voice acting rerecords.
Gearbox also tried and failed to sue the eDuke people to try and force people into buying the new version by getting rid of a vastly superior version. eDuke is pretty much the only reason Duke 3D is still relevant on PC today.
I'd pirate it on principal over getting the World Tour version if I didn't already own it. I'd gladly buy Megaton, or even Atomic, if either was available, but I'm not paying for the garbage remake and I'm starting to get to the point where I don't want to give Gearbox money anymore. I'm seriously going to have to think about whether I am picking up Borderlands 3 or not.
They are very close to ending up in my "I'd rather just not bother with dealing with their bullshit" category of publishers along with EA and Konami.
On a related note, the classic version of Shadow Warrior is free on GoG and has been since 2016.
The Blood remaster [Blood: Fresh Supply] available on Steam is also pretty great. This is easily the most difficult Build Engine [Duke 3D] game, but it's lots of fun. It's everything Duke Nukem 3D World Tour should have been.
Ion Maiden is in Early Access, but well worth your time. It's a new game on the Build Engine and basically in Sharware form at this point. What is there is really great though.
If you want something more Quake II-ish, definitely don't miss out on Dusk. Everything about that game is highly polished retro goodness. Strafe hopping is a legitimate movement tactic to the point that it's almost required on the harder difficulties. Seriously, if you're a fan of Quake, don't miss this.
If you were ever into Hexen/Heretic have a look at Amid Evil, which is another Early Access thing by people who seem to know what the hell they are doing.
A couple of other retro-ish shooters on my watchlist recently are Hellbound and Wrath: Aeon of Ruin. Neither is actually available yet in any form, but I'm keeping an eye on their development for now as both look very interesting.