How does R/S differ from E? I've only played E. And that would have to be my favorite of the beginnings of each game.
R/B/Y is the classic, so they are original, but the fact that the other games follow similar lines makes them less unique.
G/S/C are generic.
D/P/P are fairly interesting, traveling to the lake and stuff, but they are less exciting than R/S/E, which has a better story to it.
And B/W were the worst. You don't even have to leave the house and the starters are there!
I like how E's start was unique. You begin in a moving truck, which I believe is unique to all the other Gens, which start in your home/room. You have just arrived in the house, there are moving Pokemon, etc. You go to route 1, and instead of "Wait! Wild grass is dangerous!" you see an action shot of the professor getting chased by a Pokemon. You meet your starter for a reason that isn't "You are on a quest to fill the Pokedex, take a starter," which is exciting and unique, and in my opinion, the best.