I decided to go and actually count how many movies I have with the actors below. I was surprised to see that Price and Lugosi are tied for first place. These numbers take into account team-ups, cameos, legit DVD, and DVDR:

Price 42
Lugosi 42
Karloff 34
Cushing 32
Lee 26
Carradine 25

"The important question is not, are there aliens on other worlds? No. The important question is, do they have ray guns?"