[Sunred]

Quote:

Originally Posted by Switchblade

I don't really prefer one over the other. Both have been done really effectively in the past. My favorite first episode in the franchise is actually a bit of both: Kamen Rider Black, which begins with a recently escaped Kotaro running away from the Gorgom priests before instinctively triggering his first transformation.

Ditto. As creepy as it is, that scene where he goes from grasshopper man to Kamen Rider Black still is one of the best debuts ever.

As for which type of origin do I prefer? It really depends on the show.
The "I just happen to stumble upon this thing" was probably best done by Ryuki, Gaim, and Zero-One. Ryuki's was built up very well given its investigative mystery setup and was worth two episodes, Gaim I loved because of how Kouta would tinker with the sengoku driver early in the show, and Zero-One felt the most fluid despite being part of this type of origin.
The "I'm ready" was done well by Kabuto. When I say "I'm ready" I mean someone who has prior knowledge but never used it before on-screen. Anyways, Tendou appears as this enigma in front of Kagami and the viewers, cut to brief workout montage and then he pulls out the belt, cut to Kagami going "My heart bleeds justice!" only to have his dreams shattered by Kabuto Zector picking the dude that saved his wallet the other day while carrying tofu.
Last but not least, the "I already am one" was probably best done by W. We get a brief flashback, cut to some time later, and it naturally progresses to him and Philip being a Kamen Rider while trying to solve a mystery. It was just well set-up.