Our group almost exclusively plays Pathfinder. We took a break from it for a Mutants & Masterminds 2nd Edition game that was played all the way through to it's grand conclusion! This game was a blast! We all really got into it. I picked up a lot of the peripheral supplements with the idea that the mechanics, with all the genres the books covered, might serve well as an alternative d20 generic system.
The game survived some serious real-life drama that worked itself out miraculously, which included a head injury when one of the players fell and hit his head on an extremely icy driveway. And then later seeing that same player, who seemed like he maybe didn't fully recover, took it upon himself to leave the group. After that there was an extreme sense of relief that allowed us remaining members to just launch fully and creatively, giving the whole campaign an interesting and very positive result. That player aimed to derail the game each session. Even before his accident, more so after.
After that guy left, we hit that sweet spot. A group of guys that gel remarkably well, a GM who had a clear, yet also open objective for a campaign ending, a pretty solid system, a frequent (weekly) schedule with 2 and a half hour sessions- a length which works quite well for me. It was golden.
It was such a satisfying campaign that at the end all four of us players pitched in and picked up a copy of Mutants & Masterminds 3rd Edition for our GM. As a show of appreciation for his enthusiasm, and if he wanted to run another game like that!