I haven't personally stayed but the new Le Meridien/AC combo property gets pretty good reviews. Terrific rooftop bar also. Less than a block away from the convention.

The Aloft is average, a little noisy but also only about a block away.

Courtyard is in an old building right on the 16th St Mall, good character, not your average suburban CY. About 3-4 blocks away.

Magnolia gets high marks typically. Quiet(er) boutique property about 3-4 blocks away.

IMO you can skip the Sheraton (and the Westin for that matter), some people enjoy it but for me it's too much of a generic big box convention hotel although does have a great location also on the 16th St Mall & only 3-4 blocks away.

Renaissance is a terrific property in an old bank building. Good F&B options. About 4-5 blocks away.

Brown Palace is always an option if it's in your price range and is your thing. Although about 5-6 blocks away.

If you're looking for alternatives to downtown, there are 3 solid properties in Cherry Creek (JW, Moxy & The Jacquard). CC is a fun, upscale neighborhood about 10-15 min outside of downtown. Terrific restaurants, shopping, walking trails, etc.