I've been to some amazing, very out-of-the-way places around the globe, but the ones I keep coming back to should be on everyone's tourist radar, because they really are that good:
Australia - Incredible scenery, outdoorsy lifestyle, and friendly, welcoming, fun people.
Spain - A fantastic mix of cultures, history, art & architecture - plus some nice beaches, spectacular mountains, fun festivals, and damn good food too.
The Greek Isles - Hands down, the most casual lifestyle on earth. (OK, so I watched Summer Lovers on cable at least a hundred times back in the early 80s - and yes it's kinda cheesy - but the great part is, back then, IT REALLY WAS LIKE THAT! And if you haven't seen the movie, and have any interest in seeing hot young naked male and female bodies in an idyllic setting, rent it! You'll be on a plane for the Greek Isles within a week!)
A little farther off the tourist radar, and probably a once-in-a-lifetime trip:
Bhutan - A very different place in every way. Isolated from the rest of the world until fairly recently, this Himalayan Buddhist kingdom is working very hard to keep their traditional culture intact - but it is not a "living museum", as it's often characterized. These are real people who live in the modern world, with a very different outlook, namely that GNH (Gross National Happiness) is just as important as GNP (Gross National Product).