I've had every nintendo system that has existed, except for the DS, and I wanted to know if I should dive into it now with Twilight Princess or if it's too late.
Ha! It's not to late! Get yourself a copy of Twilight Princess when it launches! You'll be satisfied. You don't need to have played all the old one to play this one.
How could you have had the NES, SNES, GB (and all its variants), N64, GC and not once played Zelda?
Hey, it could happen...I think...

make sure to get Zelda TP at launch. also try to get Zelda OoT and MM (ocarina of time, and majoras mask) off the VC when they get onto it.
you're going to love zelda games

Zelda games are the pinnacle of adventure gaming. there hasn't been a [true] Zelda game that has been disappointing, and as i tell everyone, if you think the cel-shading of WW (Wind Waker) will make it too kiddie, play the game for 30 minutes and you won't even notice the cartoonish graphics. it actually makes it into a fantasiful world, which is where Zelda games have always been staged. makes for a great experience
yes, even though WW wasnt my favorite zelda game, it was still a great game nonetheless
WW is awesome though it is rather short. I can't decide if I like it more than Oot. I never played a Zelda game until Oot but I think I actually like WW more because I loved how it was just one huge ocean that took like 20 minutes to sail across and you could go from island to island with no loading times. I also didn't find all the side-quests as much as a chore as they were in Oot. Talking to all the fish to reveal your entire map was pretty fullfulling and I loved cracking open those glowing orbs that were full of items. I hope those are in TP.
it wouldnt matter if you havent played previous games in any series. TP would be my second Zelda game. but i do like to play the old ones just to experience it for myself.