Can't go wrong with a XB360 gamepad. The official ones can be a bit pricey but they work pretty well and work straight out of the packaging. Or if you can afford to, get a DS3 and a USB cable and download the MotionInJoy drivers (with the local files, of course). Right now, I'm using a DS3 for my gaming, classic and new.

Hope this helps!

EDIT: Upvote for you, newcomer! Welcome to the forums!

If you put them through Steam, the Steam controller works nicely with older games.

Mouse and keyboard. No better way to play first person shooters. Really. I mean it.

I agree but it is not everyones ideal control scheme for many reasons.

A lot of games of the vintage you are discussing are not well designed for controllers. You can use just about any controller with xpadder or joy2key to get them going, or find source ports for certain of those games that have controller support, but honestly, the games you describe are the sort of things the Steam controller was designed for.

You can add GOG games to Steam and configure them to use the controller.

If you're looking at games that are of the same vintage as what you describe, but had native controller support at release, you may be well served by a Logitech f310/f710. Those controllers have a switch that allow you to change between Xinput (the more modern, but less flexible, controller layout) and the older DirectInput.

Prince of Persia: The Sands of Time is one that has some issues with xinput controllers, but works well with DirectInput. (older games except square-gated sticks and can't always deal with the triggers-as-axis that xinput uses)

No point in using m+k if muscle memory is half the nostalgia factor for him here.

I'd recommend Logitech F510 (or the cheaper F310), since it's reliable and easily configurable. Xbox controller would work as well,but I find it a bit wonky for my taste.

Well a "reduced" keyboard-like thing for strafing and weapon selection might work. But aiming without a mouse? Mouse enables you to turn around in an instant, or follow a slow-moving target with a sniper scope. I would not like to play any first person shooter game without that kind of responsiveness and precision.

When it comes to classic FPS games, I still would recommend keyboard and mouse over a controller. But if you want to use one, the Xbox 360 controller is a good choice.

Use a Steam controller. Problem solved.

This is so true.. I don't really play FPSs any more, but I certainly would never choose to use a controller over mouse and keyboard..
I'd struggle through on a console as there is no other option, but for PC FPSs mouse and keyboard is the best option.

I should really pick up Unreal Tournament at some point...

We're talking about 2d shooters with auto aim. Controllers work fine with them.

What auto-aim? (Other than Doom up-down)

What auto-aim do you think I'm referring to? I guess iv been imagining it for 20+ years.

What about aiming left/right? Does Outlaws have auto-aim, or Shadow Warrior? If so I had probably turned it off. I prefer a) sniping/headshots and b) rocket launchers (timed leading, for maximum splash damage). Both do not work with auto-aim enabled.