It's a pretty simple answer but no, it does not. A guidebook for Dragon Ball GT called the GT Perfect Files states that he did not get any weaker. However, he does have a harder time maintaining his
To answer the question; Goku is still ridiculously strong, but God just...introduces a whole new REALM of power that wasn't measurable before. By the time he goes SS4, I would say he's at least... iunno 50x as strong as he was when he faced Kid Buu. GT is stated to be a continuation of the events of Z.
Though he briefly regains his adult body when gaining the Super Saiyan 4 transformation, Goku stays a young kid for pretty much all of Dragon Ball GT. The original idea was that this, combined with the more adventurous scope, would take things back to how they were in the original Dragon Ball.
GT Goku is so broken that he blows Super out of the water at the end of GT, even in his base form he's still one shotting a lot of the heavy hitters of late super. And even though he can't defeat people like Broly, Jiren, and Beerus in base, he can just transform.
Goku's strongest form differs in each Dragon Ball series, from the Great Ape in the original, to Super Saiyan 3 in Dragon Ball Z, and Super Saiyan 4 in Dragon Ball GT.
Goku admits that he was holding back at first only using 80% of his real power which would put Goku's battle power at 4.8 Quadrillion.
Starting off the list as Goku's weakest form is the original Dragon Ball transformation, the base Super Saiyan form. While still useful and powerful, even the mastered Super Saiyan form is the weakest of all the branch's transformations.
In the anime-only sequel series Dragon Ball GT, Goku is transformed back into a child by an accidental wish made by his old enemy Pilaf using the Black Star Dragon Balls while Pilaf was about to wish to take over the world.
Not only does this show that GT Goku is stronger (He fought people STRONGER than Super Buu in base form.) Not to mention that if it's true that Goku absorbed ALL of Super Saiyan god's power into his base form, then this ALSO shows that Super Saiyan god's power is only 8X higher than Super Saiyan 3.
How old is Goku in Dragon Ball GT? Dragon Ball GT opens five years later, shifting Goku to physically 42 but chronologically 49 years old. Emperor Pilaf steps in to complicate things even further after reverting him back to an 11-year-old while retaining his adult mentality.
Immortality: As shown in Dragon Ball GT: Hero's Legacy, Goku cannot age and will presumably live forever. It is unknown if this immortality extends to him never being killed, but he certainly has eternal youth.
While it's easy to assume that this version of Goku is the one that exists in the GT timeline, that's actually not the case. Xeno Goku's history is similar to Dragon Ball GT's Goku in almost every respect, save for a few core events.
According to the video game Scouter Battle Kamehameha, Super Baby Vegeta 2's power level is 1,300,000,000 and Golden Great Ape Baby's power level is 1,580,000,000.
Xeno Goku is far more powerful than the GT and even Super counterpart. Proof of that would be when SsjBlue Goku faced Ss4 Xeno Goku. SsjBlue is clearly the superior transformation but yet Xeno Goku was able to keep up and match Goku. The only way Super Goku would surpass Xeno Goku is with UI/Mui.
Gohan. From the very top of Dragon Ball Z, we were told repeatedly that Gohan had more potential than any character in the series. This all came to a head at the Cell Games, and with Gohan stronger than his father had ever been and Goku refusing to be wished back to life, Gohan was sworn in as Earth's protector.
This is a phenomenal display of strength, but Goku learns that his temperamental new transformation still isn't enough to beat Jiren on his own. Ultra Instinct is considerably stronger than Dragon Ball GT's Super Saiyan 4 transformation.
In a normal fight, Saitama does get stronger as he fights, but goku gets stronger on a faster rate. Goku would probably let saitama hit him a few times which would hurt him alot, but goku would get back up and probably transform to ssj3 or ssj god. The so ” ONE PUNCH MAN ” needed a lot of punches to beat boros.
Goku's training between the Baby and S17 sagas got him to surpass Super Baby Vegeta 2 in SSJ, an increase that makes him at least 64x stronger over a single year timespan (which is the length of time between Baby and S17). Multiply that by 100 and Timeskip Base GT Goku would be 6400x stronger than Omega Shenron.
However, both are considered canon within the anime. While they should be seen as a continuation of Goku's story, it is not necessary to watch either Dragon Ball Super or Dragon Ball GT. There are some great moments in these shows but they aren't required viewing for Dragon Ball fans.
Nope, it isn't
No. He was only a non-canon movie character. Since he appears in GT, that puts GT in the same fictional universe as the movies, or at least Cooler's movies. And neither of them can fit into the timeline of the DBZ manga or the series.
Re: Kid Goku's tan in GT
In a lot of the manga artwork, Gokuu (and company) are colored rather darker compared to their anime counterparts. So it isn't too outlandish that Gokuu has a tan the way he does.
Super Saiyan 3 is one of the rarest transformations in Dragon Ball history, and upon an explanation courtesy of Goku, fans know exactly why that is.
Weaker: King Kai
This was made obvious when Goku and other fighters trained under him, and became immensely stronger in the process. We rarely get to see King Kai fight, but it's fair to say that he probably has a few tricks up his sleeve. That being said, he would have no chance against Goku.