The way I see it the power gildarts displayed in the past is not even a proper benchmark of power anymore. We saw the ease with which natsu defeated bluenote, gildarts with the power we have seen so far did not manage that. For gildarts power to be relevant in a manner comparable to what it was before he needs a huge powerup at the very least. And even then, natsu has at least dragon force available to him, there is no reason for him to be weaker than gildarts if his base power is much stronger than what gildart's was 1 year ago. Gildarts would need to double or triple his sheer raw power to keep up. Of course, it is possible he did that considering grey, erza and lucy apparently did at least that over the timeskip and laxus apparently had an insane power boost as well.
Well this is basically the nuts and bolts of the equation between Natsu/Gildarts, Gildarts has not shown with manga feats that he is stronger than Natsu. However Gildarts has always been the strongest in Fairy Tail. Is it fair to think he still is top? Idk, I tend to side against him still being top given Natsu and Laxus have seemingly showed Gildarts+ level feats with less effort. I do give Gildarts the benefit of the doubt that he could improve (his mountain punch feat was better than Empyrean imo so it can be inferred that he even improved between Tenrou and Tartarus, although I am not willing to bet big on this). Did Gildarts train? With Cana possibly, but that's it. So there isn't any reason to believe he's jumped up in power imo.
My main point of my post was relative to fans however. Would it be acceptable within the fanbase that base-Natsu is stronger than Gildarts? And by extension Laxus as well. Even Gray/Erza perhaps. At the end of the day Gildarts is very much a side character, but is still considered awesome by most fans imo.
---------- Post added at 06:42 PM ---------- Previous post was at 06:29 PM ----------
Yeah, it may sound like some of us "want" Gildarts to be the top wizard still. But from our perspective, we might think others also "want" Natsu to be the strongest because he is the main character. I mean we all respect each other's opinions but at this point we still can't tell who really is stronger. Plus, like you mentioned, we also have to account for other factors like transformation. For example, I personally believe Base Natsu is weaker than Gildarts but E.N.D has to be tied or stronger than Gildarts.
Well the difference with Natsu fans is that he's shown he is at the very least on par with Gildarts(Tartarus) and likely above. Pre-Avatar arc feats you could probably make the claim that Natsu fans are hoping/wanting Natsu to be stronger, but after the feats there was proof. I don't disagree that there was a desire for a change in the guard from Natsu fans (at least some of them). Personally I am slightly more of a fan of Natsu but I wanted him to be stronger because he just had to be (to face Acnologia). That is right we cannot tell with certainty who is stronger and we're entitled to opinions (this is never a dispute), but we can at the very least suggest what is more likely and what isn't. For example we haven't seen how strong Jura is right now but I think it is more likely that Natsu is stronger because of feats, however my assertion could be wrong if Mashima allows it. Just like Gildarts. Gildarts is probably one of the few though that could actually be stronger than Natsu (Gildarts, Jura, Jellal, Laxus fit this criteria for characters from pre-TS). For instance I Midnight has nearly no chance that he is on Natsu's level, but Gildarts has the pedigree that's for sure.