Most of the X-men were about 16. I think the main Avengers were about 30, which is only 14 years older than Peter. Janet, Wanda and Pietro were only about 20.
And yeah, Richard Parker was worse than Tony. At least Tony was alive and helped him out. Peter trying to find his dead/not dead father was a lame storyline. I don't think Peter is pretending Ben doesn't exist, it's just not necessarily relevant. But if he was older, he wouldn't be looking up to Tony in that same way. Which is why I think he should be older