For me, the last time I really enjoyed grinding in my game was Grandia 2 for the Sega Dreamcast. The combat system was slick, the moves satisfying and fighting was always engaging.
This. Never as a kid, never in college when I had all the time in the world, and certainly not now. Even when I retire, or if I win the lottery and just have to sit on my ass all day, I guarantee you that I won't like grinding.
Pointless, idiotic mechanic designed to stretch 4 hours of story into 100 hours of gameplay. Bite me.
See also, MMOs. Maximum player time out of minimum development effort.
If the battle system is good then grinding is the best! Being able to jump from fighting style to fighting style without much fear of dying is really enjoyable to me; I always find that it makes me find the best weaponry and abilities to use on the fights that actually cause me trouble (if I didn't grind in Dark Souls for instance then I would never have improved my aim with the Pyromancy skills and the later more agile bosses would have screwed me over).
Also, there is an amazing amount of joy I get when I get a rare drop I was hunting for or even wasn't expecting (One memorable moment is in Final Fantasy X where I was grinding in the Moonflow to test out Rikku's Mix abilities and during it I stole enough Twin Stars to customize a Half MP Cost ability onto a weapon for Yuna!)
Grinding was cool back in the early days of school dances because it was the biggest deal to have your dick touching a girls ass, even though its through several layers of clothes. I prefer to actually try to dance now though.
Also, Tony Hawk's Underground was the last time I really enjoyed grinding.
And now that I've answered your question in order of what first popped into my head when I saw the word grinding, I'm going to answer it for real. I never really like grinding, and I almost always try to avoid it. The last time I did it was when playing Rainbow Moon for review, and it reminded me that grinding just simply sucks. The last time I enjoyed it was maybe in WoW, but probably all the way back in the Pokemon days.
In the time of Anarchy Online, 'round the Shadowlands expansion, you had to kill rocks to grind out the last 20 (of 220 goddamn) levels. And, to make matters worse, the end could really only be done in groups. So most of the rock-killing involved friends getting together, and pretty much getting drunk, and grinding out rocks.
Eventually, like years and years and years later, they implemented questy instances for Shadowlevels, and made the grinding, while not really more tolerable, more understandable.
But getting drunk with my friends, while running around in a circle, looking at rocks and pressing 12345bk 11234bkddddd was actually kind of fun, in a super nostalgic "It wasn't really fun, but whatever. Don't judge me!" way.
Dragon's Dogma was the first time in a long time I got Loot Lust and kept grinding well past when I needed to.
The Everfall and Ur-dragon instances are pretty fun. Maybe too easy especially once you top lvl 60 and/or when you start lvling up Ur-dragon loot, but the mechanics keep it from getting too repetitive like most grinding is.
These days it seems like I prefer games with a bit of grinding in them cause I always want to play while listening to some podcast or whatever, so if the game is good and has grinding I'll probably enjoy it. It can be anything from doing side stuff in Assassin's Creed to playing the recent Theatrhythm (though in that case the music is often necessary to play efficiently so I couldn't listen to a podcast whilst playing it).
In a way it makes me sad too because I have a hard time getting into games that don't have this low intensity, grindy, tasks these days. It's doubly sad because it's not like I am wanting for time at the present. There was a Extra Credits episode a while back that talked about RPG's and they mentioned the reason why grinding was enjoyable. They had a word for it but I've forgotten what it was.
Probably Dark Souls. The combat was so great and the idea of steadily getting strong, creating better weapons, was an ideal worth fighting for as I would constantly kill enemies for their item drops, head to a bonfire, then start it all over again.
Also Dead Rising games make for some fun grinding.
I am grinding right now on Dragon Quest Mosters: Joker 2. I need to if I want to beat the last boss. I enjoy it as I am constantly producing new monsters or improving existing ones. I alsways enjoy grinding. Even grinding on Gran Turismo 5 to buy all the cars didn't bother me, but mainly it is about grinding away at JRPG like Pokemon.