I tend towards the opposite end of the spectrum: long, crazy games. My current game is at 25 hours, and I'm just now getting to the AI homeworld (mostly because it took 10-15 hours to clear out the buffer planets and the end of their chains, since they had some good stuff like 2 advanced research stations and a factory, and then secure my chokepoint). Of course, I also tend to play on maps with lots of chokepoints, which cuts both ways. That said, short games are great as well, but I like the strategic planning required for winning on 100+ planet tree or spoke maps.