Prediction is exactly the way one counters Genesect, every single Genesect matchup is a prediction game for both side of the player. Basically Genesect, and to a less extent every single Voltturn user, is playing a very different game compared to the rest of the meta. Checking them is less about team build but more about mind-games.
On the other hand, every single other Genesect build outside the scarf one can be pretty much deemed inferior in general. I have yet to seen any argument about the actual execution of those sets.
Btw, I really think people should try out some other pivots, notably the TTL trial, before making quick arguments about Voltturn as a whole.
Look, if prediction is the only way to beat a Pokemon against which the risk for you (it going for the coverage move) is greater than the risk for the opponent (to use U-turn and gain momentum), then the Pokemon is utterly unfair. Technically I can beat Darkrai with 'prediction'. I can beat, heck, Mega Lucario with 'prediction'. But, when risk > reward, you cannot risk the play. It's simple risk/reward logic. What's a prediction? A prediction is a 50/50. You should only be predicting in true 50/50 scenarios, as risk/reward will guide you otherwise. And the risk of Genesect smacking your Lando-T with Ice Beam is greater than the risk of you switching to something that can sponge the Ice Beam/U-turn, and is quite possibly a stupid play when such Pokemon might be what you rely on to handle certain threats on the opposing team. Genesect doesn't have to deal with mind-games, though, as U-turn eliminates them entirely. It ALWAYS has a safe move.
Also, non-Scarf Genesect has NOT been deemed inferior. It's just the quote on quote "best set", and even that's hardly the truth. There are two variants of Scarf, physical and special. There is also the Band set, which is a freaking amazing attacker AND good revenge killer to boot due to CB-boosted ESpeed. There's the EBelt set, which is an amazing bluff and should not be undervalued. Regarding EBelt as meh is very silly, as since Scarf is so common, bluffing it is very easy. The opponent just can't risk you being Scarf, as they have no way of knowing based off your team or anything. SG Genesect, given blocks to it are removed, can easily sweep. Genesect has the strong STAB move, the coverage, and the priority to prevent revenge kills from even Talonflame. SG is probably my personal favorite Genesect set, tbh. Specs Genesect can rip holes in numerous physically bulky Pokemon that Band can have trouble with. There's also the Band set, but with a LO, that takes advantage of the ability to switch moves and poses a significant offensive threat. There's also the sash lead set, which can deal serious damage at the beginning of the game, able to any one hit right off the bat, and can U-turn to get momentum right off the bat. I just named eight amazing Genesect sets right there, that all work absolutely amazing and are insane to deal with. They fulfill all kinds of different roles and hit on all ends of the attacking spectrum. I haven't covered AV, which has received positive reviews from numerous OU QC members in the Genesect analysis, as it is able to take special hits, such as Latios' Draco Meteors, very nicely. There's some calcs/justification listed in the Genesect OU analysis thread and the Assault Vest thread here. You would have a whopping nine possible Genesects including that. It is more than BW OU Jirachi, which was commonly considered to be one of the most versatile and effective Pokemon in OU. The difference? Genesect has STAB on U-turn,
Download, significantly higher offensive stats, powerful coverage moves, an amazing setup move that also boosts Speed...a parallel can indeed be drawn to BW OU Jirachi, except Genesect is even better than Jirachi ever was.
The difference between the VoltTurn of Genesect and other Pokemon is that it has the coverage to punish everything that opposes it. Thundurus is indeed very good, but a parallel cannot be drawn to Genesect. It has worse bulk, shitty typing in comparison, much less versatility...Thundurus is hardly comparable. Tornadus-T is in a similar boat.
I am in general against the ban of Genesect....
Well, so things boil down that Genesect's only advantage against other Voltturn user is a more powerful U-turn, and outside that it even gets inferior coverage move when the prediction goes wrong(as shown in my analysis). Basically an extreme approach of offensive Voltturner in terms of both risk and reward, and we have to keep in mind how much it sacrifices for it, it is a horrible sweeper. It sweeps in Gen V simply because that was a stupid meta with everything frail as hell, which is in turn, a result of the HO nature.
The kami/cloud trial actually take a similar approach, notably Tornadus-T, which got a regenerator and is passive-damage-proof. I am now trying to replace Genesect with it on the suspect ladder with aecrobatic/superpower/u-turn/knock off, I am missing the fly gem so much....., anyway, the result is okay and it actually functions like a more forgiving version of genesect both to me and my opponent.
One side note about Thundurus-A, any earth switch in risk taking heavy damage if not OHKO from HP ice(especially when most are so frail on the special side).
Thundurus-A also has the advantage in the sense that it can invest on its volt switch, which in terms of stability may be even better than the download, another similar trait is focus miss, but ofc the risk of focus miss is extremely anti-competitive because that does not even involve mind games (though the probability probably stays similar).
Also, this gen actually gives the trial a new toy in the form of Knock off, a very spamable move.
Another note, Mega-Mene, which I just met a team built around it and does really well, is another "genesect" to be concerned, and it gets Overheat as a powerful hit and run poke. The one I met was not building things that way though.
Overheat/choice Infernape is also included but I don't think anyone is actually using it that way.
A bit off-topic, but I list out these pokemon just because I hope they are the thing you are actually comparing Genesect with, not things like utility Rotom or tank Landorus-T. These pokemon share traits which include fast and to different extent powerful hit and run, and will be backfired due to misprediction, which includes choice-locked, stat drops from superpower and overheat, or even the misses of focus miss, knock off also does pathetic damage and can mean a free switch to any Mega, especially when you are choice locked.
Overall, I personal don't see Genesect outclass them that much due the higher risk involved and the fact that it does not sweep. However I must admit the latter point may be a bit squishy, and if Genesect is actually banned, this should be the only reason.
Every single one is inferior to Genesect in some way, shape, or form, or are entirely different. Tornadus-T and Thundurus, as I've already stated, are barely comparable. Mega Manectric isn't really that good, either. It simply doesn't hit /that/ hard. It isn't another Genesect. It, like the Kami duo, has issues with bulk, typing, etc. There are also plenty of Pokemon that don't take much from Volt Switch, and are immunities to it. Oh, and another point toward the Kami duo -- they're weak to SR. This sucks hard for a VoltTurner that ideally wants to get numerous switch-ins. Mega Manectric is okay, but it's not great. Also, MixApe and CB are probably Infernape's best sets. Infernape isn't included either, though, as it lacks the STAB on U-turn needed to make it genuinely powerful. It is just fast and has nice power.
These Pokemon are also much,
much less versatile than Genesect, and have other downsides compared to it. Do you see them on virtually every offensive team? Well, maybe Thundurus on HO in this metagame (it's so good), but besides it, none of them are found so commonly. Oh, and what is Thundurus very often paired with? You guessed it, Genesect. VoltTurners are hardly mutually exclusive, and are often used in tandem. Thundurus is great, but Genesect is just ridiculous.