Some offenses are built around one player. Some are built around the styles of more than one player. Some offenses rely on the fast break, while some can set up in the half court and take their time scoring. Some offenses have one player distributing the ball to all the others, while some offenses are built on the premise that all players should pass and shoot equally well. Some offenses incorporate the three point shot into the offense, while others ignore it unless it's necessary.
Some offenses are reliant on the starters while others heavily involve bench players.
Questions that don't have good answers. The best offenses of the past decade have varied quite a bit in their styles, indicating that there may not be a generic 'best offense'. Some great offenses have had an outstanding point guard and some haven't. Good scoring centers seem to be fairly important, but definitely not necessary. Three point shooters didn't become prevalent until recently, but now seem to be common in good offenses.