Mine has to go to my guy Vision. I just recently got into comic books (early last year) and I really enjoyed from the 80's the limited series of him (?)(it?) and Scarlet Witch. And just recently Roger Stern's Avengers where Vision tries to play god link his brain up with all the computers in the world and nearly dies to bring about a misguided utopia.
I think what I like about him is that he's a robot but he's very human and loves Wanda a lot and it doesn't feel phony or forced. Contrast that to Mockingbird and Hawkeye and it's just kind of like meh.
Plus he's got rad powers too. He should join the pantheon and bad ass robots like Android 16, 17, 18, The Terminator, Johnny 5, and HAL 9000.
Off the top of the dome? I'd have to give to Ghost Rider. I have always found his power set and motivations to be really interesting when he has a decent writer.
Though I have also always been a big fan of Marvel's Space stuff. Characters like Quasar, Nova (both Richard and the new young kat whose name escapes me at this exact moment), Beta Ray Bill, those types of superheroes in the stars. I think Marvel has a lot of uniquely interesting cosmos when you get away from our beloved heroes of Earth.
How's the ghost rider from the 90's?
From what I can remember it was pretty tight, but I really started clicking with Ghost Rider in the 2000s. From what I hear from other comic dorks is that lot of his 80s stuff was pretty good too. Though I can say most any "Midnight Sons" run is good.