Black & White. Soul Silver and Heart Gold are remakes of Gold/Silver/Crystal, which means you play in the region just west of where you played the original games (Johto), as well as the original region (Kanto). While it's a great nostalgia trip, and I'm glad I've played them, it kind of has this expectation that you already know what's going on. B&W have a completely original 150, and you can't get ones from other games until after you beat the Elite Four. This makes it easier to immerse yourself in it, since there's a sense of newness that the games haven't had for a while (this is coming from one who got all 151 in Red, got bored in Gold, and didn't touch the series again until Black). By starting anew with Black or White, you'll feel like you're playing something that doesn't require you to have immediate memories of anything, but it will open you up to old stuff AFTER you've finished the main story.
i actually lie, i remember playing pearl version 5 years ago but it did very little for me. felt a bit.....meh? wasnt a fan of mixing old and new pokemon. either all or nothing. think black and white are in game sales tomorrow anyway so ill probably give white a go (most people i know have black)
If haven't played since Red and Blue I'd recommend Heartgold/Soulsilver. GSC were awesome sequels and the remakes are even better, and coming off the first gen of games they've got tons of references and throwbacks to the originals, along with being able to explore Kanto two years after the events of the first game.