Yes there can be. A developer can go overboard on each too, so something can be simple, but incredibly hard to use, or complex but incredibly easy to use.
You mentioned WOW earlier. That is actually something that is simple, but can be incredibly hard to use. To see what I mean, just take a look at the DPS statistics for the same class of character at level 110, for the same gear, same talent build, and same item-level. Obviously there's something going on when one player can have over 2 million DPS, and another player with the identical build cannot do half of that even during a burst. Some of that is preparation and their level of aggression, but don't discount the rotation they're using. Even expert theory crafters can get it wrong (Right Icy-veins?)