The Bellagio is one of the nicest hotels on the strip, but it'll appeal to an entirely different crowd than some of it's peers in the "upscale" hotel ranks. It's got a more more grown-up feeling than some of it's contemporaries and probably appeal more to business goer's than people looking to go clubbing.
Whether you are staying at the Bellagio or not, there are plenty of reasons to wander past the famous fountains and see what's inside. Restaurants, bars, a Cirque show (O) and my favorite; the seasonal gardens.
The themed gardens are admittedly my favorite part; right now they are made to look like tulip season in Holland, complete with windmills, canals and gorgeous flowers. During Christmas time they have the most amazing decorations; every few months they change it up a little and it never fails to impress.