Reading other peoples lists I think I generally find rides more re-rideable than most people.
Theres one ride which stands out though, Air at Alton Towers.
My first ride on air blew me away. Better than anything Nemesis could ever do! Unfortunately once the flying experience has been "experienced" it never lives up to it's previous rides. Every time I visit Alton Towers Air slips down my ratings slightly. Now my previous favourite ride is only "Good but not great".
And on the opposite side of the scale for re-rideability...
I'm different to the majority's opinion with Intamin top hat launched coasters. I thought stealth was kind of "MEH DISAPPOINTMENT" first time, but I've came to like it a lot more since then.
I find oblivion suprisingly re-rideable. Even after 10 rides in a row It's still just as brilliant.
Nemesis I can never get bored of. EVER!