Top Secret was fun, but it was also the kind of game that works best when you ignore 90% of the rules and just ad hoc everything. I distinctly remember doing 10 damage to a thug's head with a shotgun (this required rolling 0 for location and 0 for damage, both on a d10). Body parts normally only have 4 hit points in Top Secret....
Gamma World was all about the setting. I don't even remember the mechanics. Some throwaway D&D clone as I recall, but the setting was pretty great and focused on the bizarre and surreal.
Boot Hill, conversely and appropriately, was all about dying under a hail of gunfire. That's mostly what happened.
I never got in to Alternity, though I remember hearing good things. All I remember about Marvel was that it wasn't hard to be super overpowered. I only played WEG Star Wars. The rest I don't think I was aware of. Maybe Conan, but I never played it or saw it for sale.
Frankly, I'd rather run Savage Worlds than any of the above rules sets. Some of them have interesting settings, but I don't remember any of them having good rules. SW has great pulpy rules for these sorts of settings.
