DOSBox

[Retodon8]

Commander Keen is one of the best game series ever in my opinion!

DOSBox is definitely awesome, not crap!
xXyunaXx, DOS isn't hard to work with once you get used to it, so I suggest playing around, looking in the documentation to find a list of the commands you can use and what they do, and especially follow a step by step help document.

Also try a frontend, listed on their site.
It's a graphical shell that removes the need to type in everything and lets you use a mouse.

Jetpack's indeed a cool game, reminiscent of Lode Runner.
Also it's free, comes with a puzzle game called "Squarez", so download and try it if you haven't people!

There was a bit of controversy due to Steam/id not giving credit to DOSBox.
Actually the DOSBox license doesn't require it, so the DOSBox team was cooler about it than its fans.
There were some small issues too, fixed with a few updates.
Not sure if they fixed the fact that every single game needed its own copy of DOSBox though, but I hope they did!