Hrmm
"Good" kaiju:
-Godzilla (dur)
-Baragon
-Mothra (adult)
-Toho Kong
-Rodan
-Anguirus
Aliens, etc:
-Mechagodzilla (Black Hole Aliens)
-King Ghidorah
-Gigan
-Hedorah
-Megalon
-Titanosaurus
I'd say the earth monsters would have their work cut out for them. Although we all know Gigan and Megalon are pansies (as much as we love em). A combination of any of the others would be pretty deadly, however.