ESB was probably the best of the lot. That still does not prove that the infamous quality gap that nobody can quite put their finger on actually exists, at all, between the OT and the PT.
Basically what you're saying is that the OT's main cinematographic merit was to innovate. That I agree with. Note that I haven't been saying that the OT is great or anything. All I say is that the PT is not significantly worse. And now that SW is no longer new, logic dictates that the merit of the franchise is... nil. That is not a problem for me as fortunately I'm not a professional critic.
Also, I have a feeling you don't look for the same things in SW films I do. I'm happy with a healthy amount of action, loads of eye candy, and enough character depth and interaction to fill the gaps in between. That's what I watch SW for. If I wanted to do mental gymnastics, delight in the creativity of experimental or alternative cinema, or experience the ecstasy of a narrative masterpiece, there are many other flicks that are much better suited for that. But perhaps I don't hold the same expectations from SW as most people seem to do. For me, it's just mindless entertainment. And it's pretty good at that.