Currently I'd like a campaign with these ingridients (and others, these are just the ones that comes to mind right now):
Arcane spellcasters are few and far between. Only those born with 'the gift' may become mages, but it takes dedication and hard work. (Hmm sounds a bit LoTR

)
Less races, especially orcs, goblins, kobolds, etc. There are just way too many of those in standard D&D. I would like something more similar to the ratmen of Scarred Lands. Like an infestation growing underneath the human lands.
I might keep elves, but they should be very secretive, and known to people mostly from fairy tales. It would be cool if they were really evil and twisted

Perhaps they are the true masters of the ratmen, breeding them in dark rituals involving the sacrifice of human children. They have realized that the humans are spreading quickly, due to their much faster breeding. Thus, to keep the humans in check, they felt they had to create an even faster breeding servitor race, the ratmen.
If I keep the dwarves they should live only in a huge, and far away mountain range. They might be a dying race, slowly wiped out by a terrible disease that might eventually spread to humans, making the dwarves sort of an unwilling enemy.
I might also keep a race I made some years ago: The Giant Flying Squirrels. (I'm actually quite serious). They are forest dwellers with a strong druidic tradition, and could provide a 'different' playing experience as pc's.
Hmmm...the above kinda implies that I like Warhammer FRP's setting, which I guess is true, though I have never played in it.
I'd prefer a gritty and dark setting, with quite a bit of meta-plot in it, which might be because my current campaign lacks focus, and that can be had with meta-plots.
But, as mouseferatu said, it changes after every campaign. At some point I'd probably love a high magic campaign, or perhaps a steampunk-style campaign, with the heroes riding steamtrains, and firing muskets and steamcannons at dragons.
happy gaming everyone
darklight