Old cards still viable?

I haven't played Pkmn Tcg since I was about 10. I'm 23 now, and all of my cards are 1st and 2nd gen. Are they still viable in the current competitive scene? I also threw all of my trainers and energies away, because I was a stupid 10 year old, so I need to get new cards either way. But, I have quite a few decent cards from back then. Thanks!