Not to be picky, but I think you're only partly right.
1) The first one was great... no doubt about it.
2) The second was not (& I don't think it held a candle to the first).
3) The third was a retread of the first (i.e. make the Nazi's the villians again.... a sure-fire formula)
In fact, I think the Back To the Future followed in the same footsteps. First one is ground-breaking, second is too dark, doesn't sell as well, and the third retreads alot of the first.
Btw, the opening scenes from UHF (that crumby Al Yankovich film), had a hilarious parody of the first Indy film. Worth seeing just that 5 minutes.
Oh but the third had that brilliant stoke of casting in Sean Connery as Indy's father. He was just awesome!!
I'm looking forward to seeing them on DVD. I won't buy them, I'll just get em from Netflix!