Oh yes, forstrokes can make as much power as piped two strokes. Check out this video of two similar planes, one piped two stroke and a YS120 (supercharged fourstroke) :
http://www.youtube.com/watch?v=dburR...layer_embedded
The whining high rpm twostroke never chatches up with the grunty fourstroke, it`s all about using the right prop, the power is definately there, only at lower rpm.
I own two YS engines, one .63 and the 110, they are brutale beasts[>:]
Edit: It was a 120, not a 110 as I first wrote