DOSBox allows you to play old DOS games in Linux. It's in the Debian repository. There isn't much to it. Check out the Wiki page. Add a line to the config file to automount your DOS drive, and remember that to release the mouse you need CTRL-F10, otherwise you'll have no way of escaping the DOSBox window.
If there's an old DOS game you're particularly nostalgic about, dig it out, or check the web: many of these games are now abandonware.
Back in the early '90s, I had nothing to do and found an old 486 computer around the house that my brother's workplace had thrown out. I had a look on it and found the game Countdown. I spent hours every day moving my character around looking for items or clues I'd overlooked. (This was before I had the internet- no walkthroughs!) A couple of years ago, I discovered DOSBox and played the game again. I didn't have the patience this time to get through the game without looking at a walkthrough.
Now I notice there are video walkthroughs of the entire game on YouTube. This is the first of a series of 17!