Akira Toriyama wasn't wrong about SSJ2.

[Truhan]

Considering what the guides provide as information supervised by him, SSJ2 is twice the increase over a SSJ, but there's a certain discrepancy between power that has doubled (or reached 100%) and a fully powered SSJ. Freeza's full power has been predicted as twice the amount of his 50% state, but a Super Saiyan can reach his limit before ascending with twice the amount. What if a SSJ2 was actually a Super Saiyan that had reached his limits? (with sparks and upswept hair to match) That way Gohan and Vegeta wouldn't need further distinction between their transformations, and the Dabra argument would be over. Unless, off course, we consider that like Perfect Cell, a Super Saiyan can be fully powered with a multiplier of 80 times their base state, for example.

[Berserker1921]

I like that. It makes sense. Ssj2 could be the full power of super Saiyan. However this theory can't be applied anymore. Perhaps during the cell arc. But after the introduction of ssj3. But you can argue that ssj3 is a mutated version of ssj2 because Goku could have only achieved it while he was dead or during fusion

[h0kuten]

Goku achieves Ssj3 a lot easier in Battle of Gods than in The Majin Buu Saga, so it isn't only a form he can achieve while dead, that was the only opportunity that he had to show it.

[Kamiccolo9]

Goku achieves Ssj3 a lot easier in Battle of Gods than in The Majin Buu Saga, so it isn't only a form he can achieve while dead, that was the only opportunity that he had to show it.

He achieves it pretty easily when he's about to fight Super Buu.

[Darkprince410]

But you can argue that ssj3 is a mutated version of ssj2 because Goku could have only achieved it while he was dead or during fusion

It's never indicated that it could only be achieved via fusion or when dead. Goku's comment regarding Super Saiya-jin 3 was that the body was better suited to handle the strain of the form when dead than when alive.

Goku achieves Ssj3 a lot easier in Battle of Gods than in The Majin Buu Saga, so it isn't only a form he can achieve while dead, that was the only opportunity that he had to show it.

He transforms near instantaneously when preparing to defend himself against Gotenks Buu to buy time for Gohan to find the Potara.

[Berserker1921]

What I meant was its only possible to achieve when you have a dead body or by fusion. Because I don't see anyone else had obtained this level except for Goku who gained it when he was dead and had no strain on his body while in the after life and gotenks. He can achieve it now however it puts massive strain on his body and he is he only who can do this. With the exception of gotenks

[Darkprince410]

What I meant was its only possible to achieve when you have a dead body or by fusion. Because I don't see anyone else had obtained this level except for Goku who gained it when he was dead and had no strain on his body while in the after life and gotenks. He can achieve it now however it puts massive strain on his body and he is he only who can do this. With the exception of gotenks

Again, there's no actual indication that you need one or the other in order to reach it for the first time. Given that Gotenks was capable of it, it's very possible that it's simply a matter of being strong enough to reach the transformation. While the afterlife may be an easier place for the form to be achieved the first time, literally nothing's indicated that it has to be either there or as a fused being. During the Buu Saga, Vegeta was naturally weaker than Goku (needing the magic of Babi-di to fix that), and he never had any opportunity to train or improve upon himself between him dying and him being brought back to help fight Buu.

As for Super, it could very well simply be that he's not put in the time needed to achieve the transformation. It was likely toward the end of Goku's seven years when he first achieved Ssj3, since he commented to Buu that he hadn't had much chance to practice it, so it'd be unlikely for Vegeta, who's essentially always been Goku's inferior when it came to transformations, to achieve in six months what Goku potentially spent years doing.

With Gotenks, the ease of transforming could be attributed to him just being that much stronger than Goku normally, as well as the fact that the boys are prodigies, which would naturally carry over to Gotenks as well.

[Truhan]

I just think Vegeta looks ugly as a SSJ3, so he probably won't attempt it Speaking of Gotenks, he hasn't really turned SSJ2 before achieving SSJ3, and his hairstyle wouldn't change much from SSJ either way, so it's more points towards Akira Toriyama's original thought, with Goku being the outlier in his demonstration.

[h0kuten]

A few things here that I'd like to talk about.

a) What if Gotenks Buu reached Goku Ssj3? How do you think the fight would go down?

b) In a recent interview Toriyama said that Ssj2 & Ssj3 are just forced increases to the Ssj transformation. Hence the massive strain in stamina at each level.

c) The Daizenshuu says that Ssj3 is a Saiyan brought to his limits.
Regarding point c) I would also like to say what if Goku had limits beyond the normal Ssj2 limits and found a way to break through them during the 7 years of training that he had? Meaning Ssj3 is his own version of being brought to his limits whereas someone like Gohan needed to be brought 'way-way-wayy' past his limits to be within the Ssj3 realm of power? In short, Ultimate is Gohan's own unique form of Ssj3 because he capped out with Super Saiyan 2, at least was the implication during the Cell Games.

[Neshawn]

So if vegeta could achieve ssj3 he would be waaay stronger than goku, right? In battle of gods, most people say, when he fights beeerus he is in ssj2. Roshi said he was even stronger than goku, so he really has max out and his power level is multiupled by the ssj2 number. So if he transformed to ssj3 his power level, which is larger than gokus, if multiplied with the ssj3 multiplier. Basically I'm trying to say he reached a higher power level than someone WI,th a smaller multiplier. So is he far stronger than goku if transformed ssj3

[Truhan]

So if vegeta could achieve ssj3 he would be waaay stronger than goku, right? In battle of gods, most people say, when he fights beeerus he is in ssj2. Roshi said he was even stronger than goku, so he really has max out and his power level is multiupled by the ssj2 number. So if he transformed to ssj3 his power level, which is larger than gokus, if multiplied with the ssj3 multiplier. Basically I'm trying to say he reached a higher power level than someone WI,th a smaller multiplier. So is he far stronger than goku if transformed ssj3

Perhaps it has something to do with Vegeta's rage giving him access to his own hidden potential. A hidden potential doesn't necessarily stack on top of a transformation for power, but being transformed increases your chances of survival in case your rage should go away. That's because I don't think Vegeta has achieved a natural level to wield SSJ3, like Gohan can't go past SSJ2, but they should be able to surpass it with just their hidden potential. Let's wait until more DB Super episodes, because I could be wrong.