Super Hero Taisen GP and Let's Go Kamen Riders are crossover movies written by the same screenwriter (Shoji Yonemura) and take place in an alternate reality where the Earth is ruled by Shocker (the evil organization from the original Kamen Rider series).
OOO, Den-O, All Riders: Let's Go Kamen Riders (2011)
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Both movies commemorate the Kamen Rider franchise, featuring a crossover between various Kamen Riders from Showa and Heisei Era.
Both are Kamen Rider movies that feature a crossover between the Showa Era Riders and the mostly current Heisei Era Riders at the time the film was released.