OK...then...what about Thunder Force?
From HG101:
"The game format is completely free directional scrolling overhead stages where you fight airborne enemies and bomb ground targets in search of a set amount of hidden shield generators. Once all the shield generators in the stage are found and destroyed, the game shifts to a screen where you have to destroy a portion of a large fortress named the Dyradeizer. Once this is done, you move on to the next stage and repeat the process. . . . The gameplay is just as basic as the graphics, with the ship having an airborne shot and a crosshair for ground shots a la Xevious. Simple looking enemies and ground turrets attack you every now and then, and the stages are more or less all the same."
Its sequels are definitely shmups, but is the original a shmup?
EDIT: Or are they? I forgot that Thunder Force II also features "free scrolling" overhead sections...Is is still a shmup?