While visuals may help a game, there's also gameplay, story (if it has one), music, controls, and other things to consider. In the end its all a matter of taste anyways, as some people may love or enjoy one game and not another. This doesn't mean one is better then the other. And if one means by sales, well older games have had more of an opportunity to make more money. Speaking of old games, I've been recently going back and playing some old Sonic and Mega Man games as of late, since I still have fun with them.
One thing I should mention though that honestly bugs me, is far too many people these days talk about graphics, but don't even understand or know that they are in fact made up of multiple components. There are textures, there are models, there are other things like shaders and lighting. I'd even say animations play a part. I won't lie, I enjoy many texture replacers for Skyrim. It adds to the established beauty the game had, but it is just eye candy, and does nothing for the game play. Is it really all those components or just a part of them people enjoy when they talk about a game having good "graphics" these days?
Anyways as much as I love Skyrim and have put countless hours in it, I'm still torn on calling it the best rpg I've played more so because it felt more of an action game to me, but also because I've played many other rpg's in my life. Oblivion got me into the Elder Scrolls, and Morrowind was great too, but if it weren't for the Final Fantasy games, Chrono Trigger, Secret of Mana, and even Pokemon, etc, I wouldn't be into rpg's at all, and thus missed out on this series, and Skyrim.