As was pointed out, I attempted to actually track this in a book i wrote. Sometimes the guessing game can get a bit dodgy but a general sense, if not a specific pinpointing, can be achieved.

What I discovered is that there are three timelines.

The first is in Star Wars from 1977. Here Annikin and Vader are two seperate people--and hence very different in age. Obi Wan is about 75, and since Annikin was his childhood friend from Tatooine he would be very close to that as well; pegging Annikin's specific age here is a bit difficult but the 70-75 range is most accurate. For the purposes of illustration let's just say it was the same as Obi Wan. Vader on the other hand was "a young Jedi" as Obi Wan call him, his mere student, and would have been around 20 or so at the time he was Obi Wan's student, thus at the time of Star Wars he is about 40 years old.

TIMELINE ONE
Obi Wan: 75
Annikin: 75
Vader: 40

The second timeline was created with the combination of Annikin and Vader for ESB, though the story elements were not concretely desided until ROTJ. In this one the elderly Annikin had to be somehow reconciled with the young student Vader. For whatever reason, perhaps to better show that Vader was Luke's father by portraying him as an old man and not someone in middle age, Lucas decided to go with Annikin's age, but for some reason dropped it down a decade to 65. Thus at the time of Star Wars he would be 62.

TIMELINE TWO
Obi Wan: 75
Vader: 62

The third timeline was created for the prequels. Because Lucas now had to reconcile the older Annikin with the student Vader in concrete, literal terms, he could not have a 50-year-old student apprentice to Obi Wan, and hence had Anakin go with the original age of Vader, that is roughly twenty at the time of his turn to the darkside. But Lucas also decided to set his discovery up as being in his childhood, not adolescence as it originally was. The first draft of TPM had things sort of consistent age-wise with the first timeline, in that Anakin was 12 and Obi Wan was an older, full Jedi knight who discovers him, and with the film occuring thirty years before Star Wars and not twenty, that meant that Anakin/Vader would still be roughly 40 and Obi Wan in his seventies during Star Wars. Lucas' second draft completely changed this--Anakin was made 9, not a big change, but Obi Wan was made into a student and in fact it wasn't even he but his master who finds Anakin. Lucas kept Obi Wan as old as an apprentice could possibly be--I think it might actually have been 27 years old.

So with the third timeline created for Episode I Vader is once again 40-ish at the time of Star Wars but Obi Wan only 57 or so--not even a legal senior citizen. This made it even more bizarre when Vader is unmasked and portrayed by a 77-year-old man in ROTJ. Whatever.

TIMELINE THREE

Obi Wan: 57
Anakin: 42

The above ages I believe are what I ended up with but I am just going off memory. Its in the chapter "The Beginning...Again" in the book, near the end of the chapter.

Of course, the PT is filled with terrific images, has some nice action scenes and is overflowing with thematic meaning and layered construction. In this regard its worth at least thinking about for a few moments. But a poorly constructed plot, terribly written characters and a rather hollow emotional core cannot be ignored--the films, as dramatic vehicles, which is what they are supposed to be, not intellectual exercises for us to analyse, are failures. But they are fascinating failures. Because even "bad" films have a lot of good elements in them. The sequels to The Matrix are very similar in their relation to the original that the prequels have--the two Matrix sequels have incredible images, some terrific action scenes and are overflowing with layered construction and thematic meaning. But the characters were poorly written through much of it, and the plot badly constructed--I think both of these are much stronger than what Lucas often accomplished, but they are not successes as emotional and dramatic vehicles.

I don't think the prequels should be written off, but I don't think any of here really did--we watched them, discussed them, watched them again, analysed them and discussed them some more. That is far more from fair, and so when we continue to criticise them I don't think its as simple as us not giving them their due. The successes that the films have within them--some clever subplotting, interesting thematic construction, etc--can only entertain you so far without having an emotional or dramatic core to hook us with. Thats why we continue to love the OT but continue to criticise the PT.

Coincidentally, I just posted an article on the rough draft of TPM.


The Beginning - A Look at the Rough Draft of Episode I

To answer your question, yes, its much less screwed up than the film. Definitly imperfect but I would have rather had this version filmed than what we got.

Yeah thanks for pointing that out, the transcription wasn't typed up by me and I didn't realise how many typos were in it.

The biggest strength about this early draft is that Obi Wan is in the Qui Gon role. Its Obi Wan who uncovers the invasion, rescues the queen, meets Anakin, decides to train him, wins his freedom and presents him to the Jedi council. Kenobi has a strong relationship with Anakin as a father figure, he has a strong relationship with Padme, and he also is more developed as a character. He's in his thirties, a full Jedi, bold in many ways but also a good role model. It would have strengthened the series so much because it has a trickle-down effect into all the character relationships and into the next films, which also meant that AOTC could have been free to take more time developing characters since there was no more introductions needed. You can see in the dialog exerpts that the dialog is no better than the final film, and of course Palpatine's whole arc is non-existant--he just shows up at the end and says "hey look I'm supreme chancellor now!" But as a first draft these things obviously could have been worked out and developed, and its great the way Jar Jar is semi-normal and actually becomes a real warrior in the end battle--a character arc, look at that. Theres also some neat bits like Theed city actually being assaulted and us seeing the people suffering, and I like the way we actually witness Anakin being accepted into the Jedi at the end.
The movie is still a bit dissapointing, but only in a "well thats not as good as the OT" way instead of "what the hell was that piece of shit?". I think if Lucas gave this draft to a real writer that could have made the characters real, the plot more interesting and the drama a bit more hevfty that the film could have surpassed ROTJ.