I usually don't recommend older games, but UFO: Afterlight is a great turn based tactical game that fills in the void between the X-Com games haitus until the X-Com reboot in 2012 (also a great game). Where the original X-Com was fantastic it's just way too dated now, but the production values on UFO: Afterlight are pretty high, and the developers faithfully maintained the game so it supports 4K resolution and widescreen (menus will be pillarboxed, but don't worry, you get all your screen real estate in the actual game).

While the art assets are a little on the dated side, the game does look pretty good on a modern PC and plays well. It's an example of one of the lasting benefits of developers doing the job right the first time... a high quality game will stay looking great years after launch. This looks and plays better than many indie games published today.

Just like the X-Com games this is copying (well enough), you've got a globe (Mars this time, weird) and you build bases, send teams to intercept UFOs, and then have a nice tactical turn based battle with them. Research the aliens and new weapons, technologies and equipment as the aliens get tougher and tougher to fight. This does suffer from the "oh by the way none of your upgrades matter because mental powers trump everything"-itis that also plagued X-Com, but what can you do?

I think this is probably a little overpriced but you can get it on sale for just a couple of bucks, and it's worthwhile going through the story if you're a fan of the genre.