The poll might need to be changed because there are options missing. For example I think he's above Ajeel but below Zeref.
My reasoning is as follows: We're gonna have to pay attention to hype and portrayal, and powerscaling. You also have to think of the terrible power inflation.
Facts:
- We're talking about a continent's strongest person. I'm not a mathematician but probability, fate, chance... call it however you want. If there are two continents seemingly as big, both inhabited by human beings, if the two human beings train for the same hours a day and have similar body consitution/limitations (after all, they're both humans not different species). For example, Spain's strongest man's weight lifting is gonna be similar to France's strongest man's weight lifting in terms of kg they can lift; the difference is not gonna be enormous. It wouldn't make sense that Ishgar's mightiest was leagues below Alvarez's mightiest (not taking into account Zeref or Acno), that is, it wouldn't make sense that August was infinitely superior to God Serena, especially when August is past his prime and GS is close to it (if prime even exists in this manga, in terms of age).
- God Serena low diffed Hyberion, Wolfheim, Warrod and Jura, who were said to be Ishgar's mightiest forces after himself. Logically there shouldn't be a massive gap between the first and the second position, but apparently there is. The second strongest man in Alvarez was massively inferior to the first one (which makes no sense, again, there must be limits to that), but OK. Now, it's worth mentioning that we cannot possibly know the power extent of the GOI+Jura. Although they were hyped to be top tiers back in the day, possibly above Mard Geer and Hades, after being fodderized by God Serena we cannot fathom their power level appropriately. Especially when Jura doesn't seem to have abided by that power inflation and seems to be his same old self. It looks like powerscales prior to the timeskip were derisory, therefore it shouldn't surprise us that Jura (if he's the same as in GMG) and Makarov are fodder nowadays.
- God Serena HISTORIA (who should be around 50% weaker than the original, or more) initially overwhelmed the main cast, but was easily defeated by a power-inflated Glidartz. Assuming that Glidartz is currently above Laxus (probably) and that Glidartz mentioned that if he were alive, it'd be a high/extreme diff fight, I'm going to bet that God Serena is = current Glidartz. Current Glidartz being above Laxus, and Laxus being above Wahl, we can assume he's a high-end tier spriggan.
- We didn't see much of God Serena. We didn't see his most powerful attacks, we didn't see him going all out, we didn't even see his base magic. So anything we can say, whether to hype him or downplay him is relatively acceptable. Though I think that defeating the GoI+Jura, casually overwhelming the main cast (not hurting, but overwhelming), and receiving praise by Glidartz (if he had been alive he'd been a dangerous opponent), hypes him quite a lot.
IMO, then, he's after August, Irene, Dimaria and possibly Brandish due to hax, but I'd place him fifth. Maybe sixth if we take Larcade into account. If Glidartz ends up pushing August to a certain degree of difficulty, then my opinion on God Serena will only be boosted.