Ok so few games are good enough that I have ever gone back to them after an uninstall. Fallout (all of them)... and Dungeon Crawl Stone Soup.
http://crawl.chaosforge.org/No music, no sound, laughable graphics... but man, the level of detail is unbeatable. The difficulty curve is excellent. I'm not sure any Roguelike will ever top it. None have so far anyway.
That's my opinion of course
Anyone playing it? A new version came out that sucked me back in after a couple years of hiatus. My mighty Minotaur of Ru is currently smashing some elves down in the Elven Halls... with an axe, a sling, and a shield. Worried about end game due to Ru obliterating my ability for spell casting... going to be just melee, ranged, and wands/scrolls/potions. And Ru... who apparently kicks some serious tail.
(Last game ended my Gargoyle of Qazlal in the Realm of Zot... due to a wrong button press)