It amazes and fascinates me to find such varying subjective opinions on the concepts of what constitutes depth in a fighting game, and the concept of tiers -- though the two concepts aren't directly related. It baffles and amuses me further on how people come to conclusions regarding tiers, or when I hear that people "don't believe" in tiers or bad matchups in the first place. When I hear things like that, I frankly have to wonder if these people have ever played ST or CvS2.
Well first of all let's define tiers and how they are made. I believe a lot of westerners tend to create tier listings without using a matchup chart. The funny thing is, although I feel that this is the "wrong" way, our tier lists based on just character strength evaluations tend to be really close to tier lists based on actual matchup charts. This may be what leads people to be confused about the whole concept of tiers in the first place. But really, I feel tiers "should" be based on a matchup chart, because that is in essence what actually determines character strengths/weaknesses and likelihood of winning/losing in a tournament.
To use the most basic hypothetical example I can think of: If Ryu, Ken, and Chun-li were in a game, and Ken has really good matchups against Ryu and Chun-Li, it doesn't matter how strong/weak Ryu and Chun actually are, Ken is technically "top tier" because he has good matchups against both Ryu and Chun.
The idea that, for example, 3rd Strike Yun is top tier because of his Genei Jin super and only his super is a fallacy IMO. Yun's super is undoubtedly good, but he's not at the top of the list only because of that super, just like Ken and Chun are not on top only due to their supers. Rather, it's because they have no particularly bad matchups aside from their matches against the other top character. Meanwhile, other characters with really good supers and moves aren't placed top tier, because those characters actually do have bad matchups despite their awesome supers. A character like Akuma actually has more trouble fighting Yang than he does against Yun. And a character like Oro ends up being practically the very middle of the tiers with some pretty average matchups across the board, except where it comes to an 8:2 matchup again Chun in Chun's favor. Matchups like this effect the character's placing in the tiers despite their universal strength.
There are some games, like Garou, where the tiers reflect universal matchup ratings across the board. There aren't any particular matchups that are out of the ordinary. We see the top tiers have all good matchups against the low tiers, and the low tiers have bad matchups against the top tiers. The only thing really out of the ordinary in Garou would be Terry's particularly bad matchups against Kevin and Gato which places Terry lower in the tiers, while Grant's only bad matchup is Kain who has no bad matchups. Thus, a if westerners created a tier list for this game based on assumptions about character strength it probably wouldn't be too inaccurate, since the tiers in this game are fairly intuitive.
But that doesn't happen all the time. Sometimes strong characters with good matchups have one or more particularly bad matchups, such as in Vampire Savior (vsav). A lot of people would see things about Jedah like; him having ridiculous high/low mixups, three good command throws, space controlling projectiles, really powerful supers, and even an infinite combo. Some might even venture to assume he was top tier -- except that he's not. Just looking at the numbers we can clearly see he has really bad matchups against Gallon(Talbain) and Zabel(Raptor). Because of these really bad matchups his overall value as a character drops down a lot. You may think he's "good" because of his strengths, but come tournament time when you face a legion of Gallons and Zabels you might quickly learn that he actually has a very steep uphill battle to deal with.
Now, that doesn't mean that if you're playing Jedah that you automatically lose to Gallons and Zabels. Another thing people enjoy saying is that the outcome of a match is based more on player strength than character strength. This is partly true. Lord knows if you're Daigo Umehara and you're playing as Jedah then you can easily mop the floor with most people, regardless of who they pick. But, what about what happens when there's two Daigo's? Or rather, at least some one who is roughly as good as Daigo? I know it's hard to believe, but they exist. So in the case of Daigo mirrors, if one of them picks Zabel or Gallon while the other is Jedah, it's obvious who is going to win. Because at that point the character is drastically handicapped, and so the player is drastically handicapped too. Nine times out of ten, the Jedah will lose badly. It's almost the same as if both Diagos picked Jedah and then one of them lowered/raised their handicap setting at the character select screen.
To the players who "don't believe" in good/bad matchups, I'm just shocked. I really don't even feel the need to explain this one. How can you not notice a difference between characters? They are not all created equal. These character-specific moves are better against some characters than others, which is blatantly obvious if you've ever really played a matchup that had an 8:2 or 9:1 rating. Honestly I feel like I'm getting trolled whenever I hear a statement like bad matchups don't exist.
There's a lot of ridiculously lopsided matchups in CvS2 for example. Claw(vega) against Yamazaki is extremely poor for Yamazaki. Athena versus Cammy is also really poor for Cammy. In the case of Athena versus Cammy, Cammy is easily one of the better characters in the game while Athena isn't especially outstanding, yet the matchup is totally in Athena's favor because Cammy has no real way of dealing with Athena's c.HP. And it's facts like that which would allow us to see Cammy's true standing in the tiers, since if she has a hard-counter like that then her overall rating is going to be dropped by comparison to other characters who may not have any bad matchups at all. Though unfortunately I'm not currently privvy to a CvS2 matchup chart at the moment.
But I don't think it's really arguable that if you pick Sean in 3rd Strike you're handicapping yourself. Sure, you could beat players who are significantly worse than you, but even extremely good players will have a lot of difficulty consistently beating their peers if their opponents are constantly picking top tier characters that are able to steamroll Sean. Most likely Daigo could beat you with Sean, but he isn't likely to ever beat OhNuki, AFM, or any really good Chun while he was using Sean despite the fact that he probably could win if he was using Ken or Yun, Sean is just too much of a handicap "even for him".
So yeah, player skill means a lot, but so do character matchups. And matchups are what defines character tiers. Not some hocus pocus esoteric crap that we make up from theories.