Trying to out-do cool fights on (insert game here) is also a pretty bad idea. Unless we're going to spend a lot of time in those cool fights, it might be better to create content that we're going to see a lot of throughout the game. A new weapon class or quest line could easily make up for not having an epic boss fight. The time people spend still playing your game is time they have to tell their friends what game their playing, and how expansive it is. Cool boss fights are a dime a dozen.