I'm the same way. When I ran
Shadowdark I knew it was a one-time thing before I started.
Right now I'm gearing up for another superhero campaign but I have two systems I'm debating:
Champions Complete or
GURPS Supers. The debate made me start this thread because I want to make sure I have the right system. The two systems are a lot alike (heavy SIM, point-buy) but Champions has a level of stat-track that can annoy me. I don't want to get months into the campaign and change my mind so this will be a long debate