So you're traveling to India; you look up the hotel ratings and reviews mentioned on your favorite travel sites, and are surprised by how affordable a nice three-star or four-star hotel seems. Why, even a five-star hotel isn't all that expensive. You go in expecting something like Caesar's Palace in Vegas; instead, the hotel seems quite, quite dated. The carpeting in your room is filthy, there are damp patches on the walls in the bathroom, the service is clueless and there are millions of bugs in the hotel pool. How does this happen?
It's just that the star rating system isn't a consistent one around the world at all. If you're traveling to some countries in Western Europe for instance, if a hotel has five stars, it only means that the rooms are at least 15-foot long and wide, that they have a good reception desk, and that's about it. Sometimes, these hotel ratings and reviews change from one town to the next in the same country. In the US on the other hand, a five-star rating means the world when your car pulls up, the perception people have to fall over themselves to demonstrate their eagerness welcoming you, there have to be wine tastings, and so on.
In some countries, the rating system is run by the government; in others, there are private companies that take care of it. Sometimes, it's up to the hotel booking sites, and so on. The European Union is coming together to bring a little consistency across Europe though.
For the most reliable hotel ratings and reviews, you want to go with a private company rating system the Forbes travel guide and the AAA are good examples. They've been doing this for at least 50 years now, and they keep updating their reviews from time to time. You can see some astonishing levels of detail in how they rate hotels right down to the number of towels folded up in the bathroom and the number of minutes room service takes. Basically, the hotel inspectors these rating agencies send out rate hotels on hundreds of points before arriving at a verdict. Every hotel comes with a review that runs to 100 pages. If a hotel, according to these rating companies is five-star, you can expect to be treated like royalty.
Hotel booking sites are pretty good too. But they aren't going to bring the kind of attention to these things that the private rating agencies do. They don't really operate in a transparent manner either. And they use different standards for different countries. But they tend to be quite good overall.
User-generated reviews like those found on Trip Advisor can be very good; of course, Trip Advisor can't verify them everything that gets submitted. If you will take the trouble to read several, you should get a meaningful idea overall. But in general, you get some pretty good advice. As for the government-rated systems like you find in Europe, it's difficult to tell. Governments are not going to want to run down their own hotels.