Lord Bills is the first "God" to appear in the series. SSJ4 Gogeta is not a god and can't reach the same abilities as bills. Remember what they said in the movie. Just because you power up and become stronger DOES NOT mean you are at God form.
Are you kidding? Kami was. His name means "God." Then Goku got stronger then Kami, the guardian of the Earth and had to be trained by king Kai. King Kai was stronger then King Yama who is the "God" of death who judges where souls go. We then find out later King Kai was the god of northern quadrant. Then we got introduced to the Grand Kai who is in charge of them. Then in the Majin Buu saga we met the Supreme Kai's and the Elder Kai. They govern the Quadrants of the universe. Supreme Kai was the ruler of the Eastern Quadrent and Majin Buu killed the other 3 and the Grand Supreme Kai.
Every single one of them are portrayed as "Gods."
"The Kais and Supreme Kais seem to be based on the deities who watch over the cardinal directions in Hindu scriptures (guardians of the directions) and Buddhist faith (Four Heavenly Kings). There are generally four main guardians, sometimes eight, with two additional guardians who govern and protect space, for a total of ten gods (like the Kais and Supreme Kais)."
They are based on real life religions of "gods." You can't discredit them and say they aren't when clearly the manga and the anime say they are.
Which brings me to the point of me typing all of this.
Being a God is DBZ means shit!
The Grand Supreme Kai was said to be on par with Kid Buu and 1000 times stronger than Frezia. Goku was about that same power at the end of Z.
Basically SSJ3 Goku was stronger than pretty much every "God" in DBZ until BOTG's was introduced. Then Bills comes along and makes Goku look like a fodder. That doesn't mean Goku was just a mortal and couldn't hurt Bills because he was a "God." Goku was owning gods before Bills was in the picture. Having "God" in your title doesn't mean much in DBZ.
Just like SSJG doesn't mean he now has the powers of an actual God. It is just a name. He just got as strong as a 70% Bills.
Basically the power scaling in GT was insanely ridiculous. Goku in base was fighting evenly with Ubb who was as strong as Majin Buu. Remember in DBZ it took a SSJ3 Goku to fight evenly with him. That means Goku in base in GT was as strong as SSJ3 in DBZ. Now you add SSJ4 to that, + Vegeta as a SSJ4 and get something the likes no one has ever seen in DB.
SS4 Gogeta is way stronger then anything in Z and only Bill fanboys won't admit it.