I'd say Eugenie Levy is probably better known than Biggs. At least that's what I'd think. Then if you don't know who Stiflers Mom is you've lived under a rock for far too long. You may not know her name, but lets be honest it wasn't her name you were watching it for.
Eugene Levy is WAAAAAAY better known than Biggs. He was in SCTV and tons of movies. Sadly, he was also in all of those non-canon American Pie movies too.
Go watch Best In Show it has both Eugene Levy and Stiffler's Mom in it, and was much funnier than all of the American Pie movies. After that, go back and watch the rest of the Christopher Guest movies (Spinal Tap, Waiting for Guffman, A Mighty Wind, For Your Consideration). Some of the best comedy out there.