If you're on a budget, then the chain budget hotels are all pretty good in Bristol - Travelodge, Premier Inn, IBIS, Holiday Inn Express. Boring, but predictable and reliable.
The City Inn is very popular with guests, being contemporary and relatively classy. (http://www.cityinn.co.uk)
The star hotels in the city, Marriot Royal and Hotel Du Vin live up to their reputations, even if they'll burn a big hole in your pocket. The Mercure Holland House is new, but getting a good reputation.