If you judge Runescape based on graphics, then yes, it will likely lose in regards to other MMO's.
However, if you take Runescape for what it is (a free, easy to pickup, non-hardware-intensive MMO) then I think you will find your mind much less filled with hate.
"Best", "Worst" and the like are all words with no factual backing. I could say WoW is the worst game ever just because I feel like it, its not a fact.
I think its good that Runescape is so easy to pick up, mostly free and satisfies the basic needs of MMO players. Compared to similar titles, the amount of investment in terms of money, time and learning are much less.