Excelsior Phase One Lysandia - Ultima clone I played with a bro way back (it was shareware off some floppy). Yeah might sound weird but back then we didn't have access to games as easily as today, I'd never heard of the big-name CRPGs and this was the first time ever I invested in stats, typed command lines, fought enemies for XP, loot and gold and explored a cool open world with quests and puzzles. Eventually came back to it as a grown up (supposedly) and finished it, great fun, I'd still recommend it.
I had Wasteland and Crescent Hawk's Inception on C64 when I was a kid. Not that I knew shit about how to "master" or beat them, but I had lots of fun with them anyway.