This isn't a "should they age" thread, or a "what fits in their continuity" thread. When you look at the characters in the titles you read (or remember), without doing any math, how old do you figure that they are?
For me:
Captain America is about 35
Iron Man is between 40-45
Thor is at least 1500 years old, but looks about 35
Hank Pym is about 45
Janet Pym is about 35
Hulk is about 50
Hawkeye is about 30
Quicksilver and the Scarlet Witch are both 28-30
Mister Fantastic and The Thing are about 50
Invisible Woman is about 30
Human Torch is about 25
Spider-Man is about 25
Daredevil is about 35
She-Hulk is about 35
Cyclops is about 30 (these days)
Professor X (would have been) about 60
Wolverine: there's no telling but he looks just about 40
Nightcrawler is about 28
Storm is about 32
Colossus is about 26
Shadowcat is about 22
Banshee is about 50