They follow on from Playtech's totally awesome Gladiator slot which you can also play here although I have to say The Hulk and Iron Man probably don't quite match Gladiator for excitement, mainly because the free spins bonuses don't seem to have quite the same level of potential but they're still better than 99% of the online slots out there for playability.
I've said elsewhere that I would really love to see Iron Man 1 and 2 & some of Playtech's Marvel slots put into kiosk versions and released at land-based casinos as I really think they would give games like the popular Book Of Ra and IGT's prevalent Pharaohs Fortune a real run for their money.
Don't forget to check out some of the other Playtech games and Marvel slots from the Games Fruit Machines Homepage.
