I'm playing Dragon Quest 2 right now, and while it isn't quite as good as it's sequels, it *is* really fun when it comes to leveling up.
I always start off with running around outside of Midenhall Castle until I reach LV3, then I go "yay! I'm strong enough!" and head for Leftwyne; then I fight around close to that town until I reach LV8 and can afford the über-equipment in the town.
And so on!
I would do this in almost every RPG for the NES, and while it's usually required, I tend to find it really fun; you really get the feeling that all that leveling up actually has a purpose.
You could get slaughtered by T3h Killer Monster, gain some levels, and then suddenly slaughter T3h Killer Monster yourself in return, as thanks.