On my opinion of rules complexity: I feel one should have as much complexity as you need to appropriately model the playstyle of the genre. For example, any version of D&D has too many rules for a swashbuckling game. They're simply too complex to encourage the style of play the exemplifies swashbuckling games. Contrary-wise, D&D of any version simply doesn't have enough rules to accomplish what Exalted or Rifts expect from their genre's.
Art from GIS for rock paper scissors