those numbers where examples, the point is performance will become increasingly smaller as issue (given the same game engine), and graphics will increasingly get a bigger issue over time.
ofcourse in general graphics influences the fun-factor less then performance (when performance is bad, fun is reduced alot more then with older graphics) while lotro and warhammer do have amazing graphics it doesnt keep me there playing. however there is like a minimum acceptable graphics-level that varies with every individual for an online game that requires a monthly fee. this minimum level goes up while technologies improve over time.
im talking in general here, and there are ofcourse exceptions to this rule, and other factors that outweight it (like a person that just wants to play a dragon for example)
WoW became big by performing good on old machines, while appart from being cartoony it doesnt offer anything very special or that is not in other games.