Hello all, not sure how much my opinion will be taken into account seeing as I'm fairly new here, but I just wanted to weigh in on my opinion on the order of the s rank mons. I agree with meteor64.
I believe gengar should be the next one after Tyranitar. Gengar to me is kind of the face of the ADV OU metagame, even though tyranitar is the most dangerous mon, it is almost impossible to find a team archetype that you couldn't fit a gar onto. Sure it's lack of special stab and frailty can be an issue, but it's amazing coverage, access to some extremely dangerous support moves, and awesome unique typing more than makes up for this. With proper investment, the frailty can be patched up to an extent, and it doesn't usually miss the loss in offense. The fact that gengar is really the only good ghost type in the metagame makes it almost a necessity on stall teams (unless you want to use dusclops for some reason) as it is really the only good spin blocker. Sure dusclops is bulkier, but that spikes vulnerability and lack of speed or offensive pressure make this rather pointless. In this role as a spin blocker, it can still function as a late game cleaner, as well as an offensive threat, and the bulky taunt + willowisp set is in my opinion the best special spikes abuser in the game. It is not limited to this role however. It can function on CM offense teams as a great lure for special walls, and explode on them. Even on teams that don't require a lure, it can still pull off an all out attacker set that really threatens teams lacking in a dedicated special wall due to it's amazing coverage and speed, and the hypnosis set rivals aerodactyl as one of the best 'pull a victory out of your ass' late game cleaners.
Celebi after gengar because it is pretty much the definition of versatility, base 100 stats across the board mean it can do pretty much anything. It can be a decent support mon with heal bell, perish song and leech seed, it can use a defensive calm mind set with leech seed making it one of the best snorlax counters in the game, it can baton pass calm minds, swords dances, and subs, my personal favorite is the subseed baton pass set which grabs tempo against special walls better than any baton pass user in the game, considering it can actually switch in on them, and sub seed lock them before baton passing to a counter, which jolteon and zapdos can't really do. Finally the offensive cm set is in my opinion the best offensive calm mind poke there is. Stab on two of it's attacks, amazing coverage, good bulk, natural cure, and even a pseudo recovery move. The only "super" poke that really gives it competition is superachi, thanks to its toxic immunity. The main issue with celebi is dugtrio, and the fact that every one and their dog has HP bug on a ton of their move sets, but even with this, it's bulk allows it to get around this sometimes. The main reason I chose gengar over it is because gengar's niche as a spin blocker is far more important to this incredibly spikes based metagame than anything celebi does.
Suicune i think should be the last mon in the S rank. It is definitely a great poke that belongs in the S rank, it can out stall a lot of its counters thanks to pressure, it's amazing physical defense, and calm mind, and subcune is extremely dangerous if the opponent makes a mistake in assuming what set it is. There are two main problems I have with it. The first is that it is vulnerable to both spikes and sand, and on top of this has only rest as a recovery move, and is usually meant to check a wide range of physical attackers. Suicune is pretty useless while it is asleep, so with spikes down, it has a really hard time coming in again, and sleeping off those turns to become useful again, meaning during those turns unless you have two waters, those physically offensive pokes can run rampant on your team. You can run the restalk set, but this either gets rid of some of its utility by forgoing roar, or some of its most dangerous qualities by forgoing calm mind. The subcune set also has similar issues, except worse since it no longer even has rest, and substitute is wearing it down further. I often find subcune to be far less valuable when sand is up, simply because it can't recover off the damage from those subs, which kind of ruins the whole purpose of being able to sub up on defensive mons and bulky waters and setting up while they try and break it, because by the time you're actually set up enough to do anything, you're already at pretty low health. Don't get me wrong, it's still great and i've had a lot of success with it, it just becomes a lot easier to play around when two extremely common environmental effects, spikes and sand, severely decrease its utility. The second problem i find with it is that it is somewhat one dimensional, you're really only going to see sub cune and defensive cune, sure there's variation in defensive cune sets, but there are like 3 viable moves for the 4th slot. Also the only attacks you are ever going to see on it are surf, and ice beam, and occasionally hp electric, leaving it easily walled. Still its ability to beat a lot of its walls in the long run thanks to pressure makes it a great mon as long as it doesn't die to spikes in that long run.