Just how powerful is Gohan by the end of the Z story?

[jackjack]

If we follow Toriyama's answer seriously, then its possible that Goku surpassed Gohan by the end of the series by whatever reason (maybe because Gohan didn't train during those years, ending up losing the power that the upgrade had unlocked, while Goku still trained everyday).

He only says "pure strongest".

A quote that doesn't exist anyway.

[Chou Gohan]

Maybe they thought that Gohan lost a certain amount of his power in the 10 years after Boo and that's why they decided to make him go SSJ in GT again.

You're giving Toei too much credit. Mystic Gohan would've made Goku worthless, so they destroyed him. See also: Gotenks.

Neither Gohan nor Gotenks made Goku worthless in movie 13. Nowhere was there ever a rule saying that fan-boy beliefs about how certain characters match up must be followed. So if there was a reason why Gohan went ssj again, that wasn't it. Perhaps the folks behind GT just forgot about it like they did several other things. lol

[goldsaint13]

Beside movies and GT crap, I think that Gohan didn't lose any of his Ultimate power by the end of Z and he was still the strongest, but somehow retired from fighting (he didn't partecipate neither to the tournament), so, not counting Gotenks, Goku was the strongest active fighter, although his power shouldn't have increased on base form by much, his true improve should have been the full control of SSJ3 power even as a living being, all to be prepared to face Kid Buu's reincarnation 1 vs 1 and being able to defeat him without the help of Genkidama, Gohan/Gotenks or Fusion...
But I don't think Gohan had lost anything... He could still transform into "The Strongest Warrior" form instead of transforming into SSJ (GT totally failed on this point and on many others), and thus being able to kick anyone ass, with the exception of any Goku + Vegeta Fusion...
Who knows if Uub could ever equal Gohan with training and if Goku actually had the idea to bring him to a such high result to make him the true hero of Earth (Gohan is incredibly strong but not as much reliable... Goten and Trunks even worst than him)...

[Fox666]

I doubt you can have fully control of Super Saiyan 3. There will always be a limit of 5 minutes

[goldsaint13]

I doubt you can have fully control of Super Saiyan 3. There will always be a limit of 5 minutes

At least he could manage to keep the max power for those 5 minutes...