UO doesn't have to be a grindfest, but it can be. For instance, try getting your magic resist to grandmaster level legitimately. Yeah.
I pre-ordered the collector's edition of this game back when it first came out. I think I was 14. I proceeded to play it every day all day for four years, riding the ups and downs of skills, before minerals were introduced, back when it was a -REAL- grindfest. My friend and I would grind mobs all day every day trying to raise our swordsmanship (this was before they presented skills with decimals, just whole points for us), and we had a contest as to who would make it to journeyman first. Took us over a week... And about three months into the game or so they introduced a patch that made skill leveling easier and we did in an afternoon what we had been trying to do for a week.
Anyway, as I said, you don't even need to do that to enjoy it. At least, you didn't have to. Some of my favorite times was exploiting the guards. =P Running into the caves near Minoc, stealing some poor miner's ingots, running into the guards, getting attacked by said poor miner, and then collecting the stuff from his corpse after the guards killed him. Good times.
Or when they implemented the whole criminal/moral system, wearing next to nothing but carrying a spear of vanquishing with me so the hammer wielding miner would get a surprise. rofl XD pwned.