I think there is no "best gambling site" that suits everyone. It is a matter of personal choice. A good dev team that gives tons of new events and promos, a friendly community are what make me stay at a certain gambling site.
I agree with you, there's no best gambling site... it's really a matter of taste, what some people prefer and what do they like! I like casinos that combine everything in one place, sports, slots, in-house games. Like others, I like it when the casino is paying attention to players, when there are promotions, some bonuses, drops, etc! I am active on Stake, Wolf, BC, Betfury... occasionally I play in other casinos if I get attracted by some nice promo! If I need to choose one as the best one I think I couldn't do it, each of them is attractive and I have fun on all of them!