This review on Goodreads mentions most of the elements you mention:
"I think it is a graphic novel" - It has illustrations.
"Earth makes contact with space-faring travelers, and they are dinosaur-ish creatures" - Check.
"The first contact is peaceful" - Whilst I can't find explicit proof of this it appears to be the case.
"Then war breaks out and humans need to fight back a technological superior adversary." - There is a war and the dinosaurs (Nitolans) are a technological superior.
"Maybe there were superheroes in the mix." - The review mentions the possibility of telekinesis so could be where this is coming from.
It was hard to believe that Barry Longyear, the author of “Infinity Hold” and “Sea of Glass”, both of which I LOVE (love love), penned this banal, super-white-bread tale of dinosaurs arriving in their spaceships to reclaim the Earth they left so long ago. It read like the script of one of those cheesy ‘Amazing Stories’ or ‘Outer Limits’ television shows from the 80s. The illustrations were pretty awful, too. The dinosaurs looked like creepy anorexic chickens and the human protagonist was a strange boxy capsule with legs. Don’t get me started on the two-dimensional, clichéd, 80s characters. Of course the humans win, despite the Nitolan’s overwhelming superior technology (or telekinesis, I couldn’t really understand), because the dinosaurs don’t understand humor… Wait, What?
The generous white borders around the text, the illustrations, and blank pages still barely make this story long enough to be a book. Rightfully, it belongs in an anthology. A really dated anthology that no one will ever read again and ends up gathering dust on a shelf in Goodwill. Seriously Longyear, did you really write this?
The only thing I can't track down a reference to is the part about what we use for fuel but this matches enough already that it is worth mentioning.