Personally I have a taste for Ragnarok and Alphaman, but I have tried them all and gotten a kick out of it.
Ragnarok I feel is very fun but horribly imbalanced, though the fun is mostly due to the setting. Also I like to think of it as being one of the easiest on the eyes, and a great introduction to the style.
Alphaman I felt was downright cute with the mutations, just like a mini-lottery, and the color scheme seemed to fit perfectly.
I still play Rogue from time to time, mostly because I keep getting my ass handed back to me in short order.
The main reason I got into these games is because any computer could put out enough power to run them, along with the file size being tolerable even on the lowest baud modem.
For those jerks that haven't tried them yet, go to the
ROGUELike HomePage to get a start. I'm not really 100% on the status of these programs, in reference to them being the latest, but if you need more than the name of the program, fuck off.