I wouldn't want to mention any specific site, as the OP was too broad...
It largely depends on the type of sport you want to bet on and also the championships you are following.
An analysis site that may be good and quite accurate for football may be terrible for tennis, for example.
In addition to these ready-made analysis sites, I also really like following tips from commentators and opinions from other people who don't bet, people who simply do their analysis out of passion for the sport without the commitment of trying to make money from it, I think this type of analysis is very important.

Anyway... some sites help, but they cannot be the basis of your bet.