The best known of the consumer review sites is TripAdvisor, but Google, Hotels.com, Expedia, Facebook, Yelp, and many others can be sources of guest reviews.
TrustYou aggregates and crunches reviews from multiple sources, and then offers a brief, mostly numbers-driven summary.
TrustYou presents an overall score (the "TrustScore") up to 100, assigns a grade (Excellent, Very Good, Good, Mediocre, Bad) and then supplies percentages (good or bad) for specific features such as location, rooms, service, food, bar, internet, etc. under a "Tops & Flops" heading.
When you want detailed reviews about a specific hotel property then you'll need to read the individual consumer reviews (or ask other travelers or a travel agent), but if you are looking for a sense of a hotel's overall score on the most important features, then give TrustYou a look.
To get a sense of the difference between TrustYou and TripAdvisor, take a look at the TripAdvisor review and the TrustYou "TrustScore" for the Palace Hotel in San Francisco.
TrustYou makes money by providing reputation management tools to hotels.