I think Partypoker. Nice site where it is possible to make a custom background and there is decent traffic. If they did not give some people an unfair advantage by allowing them to download hand histories while not allowing it for other people, I would give it 5 out of 5 stars. Pokerstars was the best but after Amaya took over it is slowly getting worse and worse to the point that some people have trouble even running the software. I suggest to stay away from that shit. 888 might also be okay but I don't like that damn casino advertisement on the tables. Also every time I log out a message saying something like visit our casino. I don't like ads. Especially not for casinos.
If the question is computer graphics, it is pokerstars, but in terms of gameplay, I cannot inform you, because in pokerstars I sometimes have the notion that I am playing against bots, because in some ways things happen to make me lose.
in my opinion, i am micro, and i played in several.
the site that I like the most and I also think that you are playing decent poker if you have good results is called america's cardroom.
for me the best.