overall though, i think any pokemon game you decide to check out will be worth the money and effort. they're all really great games and while not everything is always in my taste, i can't say i've ever played a pokemon game and didn't have a good time.
This is pretty much the best thing said.
I've had fun with even my least favourite generations and games. There hasn't been a time in recently memory where I've played a game and told myself that I truly hated the experience. Even BW, the game I feel I liked the least due to its lack of a solid Battle Facility, I had fun with because of the story and characters.
So really, you can't go wrong regardless of which Pokemon game you choose. I do want to caution though that R/B aged terribly over the years, so that's something to be mindful of if you're going for these games. Yellow is a bit better on the visuals though, and If you're wanting to go for Gen 2, I'd strongly recommend Crystal for probably the best experience, although G/S aren't bad, either. ^^