I voted litwick line. But I admit it was close. Also, haunter is best. But the poison type on the original line pales compared to the overall package of coolness that is ghost/fire --- Tired of photobucket and imageshack? Ask me about dropbox.
Gastly line since it's not weak to Stealth rock...and 3rd gen Gengar was pretty awesome with those elemental punches...on top of that...2nd gen gastly line was my pokemon catchers expert...the legendary beasts are difficult to acquire without them...
EDIT: Gengar, unlike Chandelure...isn't weak to earthquake due to Levitate...that's:
Gengar: 2 Chandelure: 0 --- Lord of gaming!!! (probably)