I don't consider the comics to be the ultimate expression of every comic book character, no. Every character is different. For most characters, who haven't seen a screen yet, the comics are still the definitive, as well as for supporting and B, C, D list characters who have received much more development on the page than the screen.
For the A list heroes?
Superman - Christopher Reeve is still the definitive, and the influence of that Superman is still pervasive, and his attributes are still considered Superman's attributes, even though no modern Superman has many of them.
Batman - Kevin Conroy has defined Batman for technically two generations of pop culture enthusiasts. Few protested that Bale would be replaced, his Batman was largely a passenger in his own epic. Contrast that with Michal Keaton who was the definitive Batman being replaced and nothing but balking. But everytime an animated feature without Conroy comes out, it falls flat, and one can even consider BTAS influences in future Batman works, from a quasi-serious mysterious origin Joker, to a best friend Harvey Dent, to heroic Catwoman, mentorship by Ra's Al Ghul and more.
Spider-Man: This one's harder, but the comics still seem to be the definitive Spider-Man, simply due to the breadth of how well and how consistently Spider-Man, as a character, is developed. Many icons and paragons are delved into, but Peter Parker is allowed to be a full person on the page, and not really in either movie series, and not quite in the cartoons either. If Spectacular Spider-Man had carried on to BTAS-like lengths, it could have been a contender.
Iron Man: Robert Downey Jr. Is there any doubt, at all?
Wolverine: Hugh Jackman. Unfortunately. Wolverine's hardly even short anymore in the comics. Oddly enough, this is also the definitive versions of the rest of the X-Men, including and especialy: Xavier, Magneto, and Mystique, with the possible exception of Storm, who is rich in the comics, had some mainstream recognition and also is all largely undeveloped and uncompelling in Fox's X-Men.
Hulk: Too close to call. None of them have made a deep impact. Ruffalo could easily take it if he keeps it up.
Thor: The movie. The comic is too obscure and has never been popularized before.
Captain America: The comics are still definitive, because Captain America started out on such weak footing in the MCU (the least profitable and least favorite of the Avengers), while TWS has done a lot, Evens, in part due to his start and in part due to his soon departure may never be the definitive Cap.
Fantastic Four: Comics are still definitive, and may always because the concept, imho, is inherently and fundamentally silver age. This is the same reason most of the DC has their definitive version in the comics.
Green Lantern: Comics, by far. The movie tried to capture that too much, imho. Hal is so defined here that the GLC didn't even change during the sweeping continuity changes of the New52.