I've had big problems with how old Anakin and Obi-Wan were supposed to be in the prequels...which I feel has led to a rolling stone of other problems (mainly in 1 & 2).
Based on apperance I'd have to say Obi-Wan appears to be 70+ in ANH when he dies. And Anakin in ROTJ appears to be 50+ when he appears as a ghost.
Going on those assumptions and the roughly 19 year gap between PT and OT, my guess is Obi-Wan should have been at least 50 years old in ROTS , and Anakin 30+.
I think by Lucas making these two characters too young in the PT, he really short-changed the stories for I & 2 and in turn effected Episode 3 to an extent. (below)
And as I've said before, Lucas turned two classic OT characters Yoda & Emperor, into cheap entertainment devices with their uncharacteristic lightsaber skills, Yoda is hardly unconfrontational...A Jedi uses their power for Knowlege and events never for attack..... tell that to Yoda while he grabs his little green stuff, poses like Jet Li, and flips around with a bad attitude....So much for the image I had of those two being like mystic sage's, using their knowlege, and having powers above fighting and flipping.
And as far as some things that people wanted to see in the prequels:
The relationship between Anakin and Obi-Wan: Basically non existant in TPM, since Obi-Wan didn't even discover him, and then in AOTC Anakin was busy trying to overcome Padme' with crappy romantic dialogue. Only in Episode 3 do we get a taste, and Obi-Wan is sent to deal with a loose plot point in Grievous for almost the entire film.
Anakin, Bail and Kenobi's exploits during the Clone Wars: This was mostly explained away as happening between 2 & 3, and Bail is thrown in rapidly to fill plot points....I won't even get into the Clone Wars itself, just the fact there needs to be a cartoon to explain things, says enough...
The rise of the Empire: Way too rushed, in ROTS, we see order 66, and a declaration of a new Empire from Palpatine (duing a Bush imitation), and before you know it we see Star Destroyers and Vader standing on the bridge looking out onto a Death Star in construction...
The manipulation and fall of Anakin: Luckily this is a strong point in Episode 3 as far as getting extended dialogue between Palpatine and Anakin, some of it is pretty good, but again considering the amount of carefull manipulation Palpatine has done up this point, he is quick to throw "I know the darkside" at Anakin, and I don't think it's a very feasable fall to the darkside, I love my wife, but I'm not sure that I would turn into a massive child serial killer for the chance of "possibly" saving her life, even if there was a 100% guarentee, I'm pretty sure she wouldn't be for that option either...Is it even possible to die from a broken heart?
The force ghosts: After ROTJ, I didn't know what to make of that, weither all Jedi had the power, it only lasted for a certain period of time or what...All I know is Qui-Gon discovered some secret and told Yoda...who told Obi-Wan....Safe to say it's still not explained.
the extinction of the Jedi order: Palpatine I guess had some trigger called, order 66 (homage to 666?)ingrained into the Clones while they where being made (sponsored by the mysterious Sifo Dyas) , they then proceed to kill off almost all the Jedi in what seemed like a day. Anakin kills children, and the Clones kill most of the Jedi....shouldn't that have been turned around? did we even need to see Jedi children?.
All of these important plot points to the OT seemed rushed, unsatisfatory in explanation or explained away as happening between Episodes .
I'd like to here some other takes.