In my opinion, gen I isn't a good place to start pokemon. Unless you're Hidenori Kusaka, at which it's the BEST place to start. Neither is gen IV/V. Where, then, is the best place to start?
Gen III, that's where.
As of 2012, Gen III is right in the centre of pokemon. It's also where I started playing pokemon seriously(The first game I picked up was Crystal, but I didn't play for real till I bought Ruby version).
I can say that Groudon became one of my favourite legendaries after that. It still is.
When you play from the viewpoint of a Gen III-er, you can look back at RBGY and GSC, appreciate the old times, and run through the beauty of pokemon's history back on the Black-and-White screen. You can also look forward in amazement at the new, upgraded artwork, regions, storyline, and everything that is found on the DS games, like DPPt, BW, and B2W2. And finally, you go back right where you started off, saving Professor Birch from the Wild Poochyena and starting your pokemon journey. It's marvelous.
That's what it's like for me, and that's what makes me love Pokemon all the more. Gen I, II, III, IV, V, and so on forever!