No, it's more like I bought a game with all the characters, I prefer not to have it held away by some inescapable skill-plateau that cannot be achieved without memorizing a bunch of combos and lowering the difficulty to it's lowest. Not all players play the game to become twitch crazies.
No it doesn't, it doesn't add replay value, it adds frustration. They're holding back a significant piece of the game, namely, actual fighters, behind a wall that, to the uninitiated, is like a mountain.
If they want to add unlockables for "replay value", then do something else. Soul Calibur 4 is a great example of this. The characters there are all unlocked by simply beating the arcade mode a few times. That's it. No perfecting, no combo finishes, continues allowed.
But that game has far more replay-ability than SF4 does. There's a ridiculous amount of character clothing, weapons, challenges, etc. Some of them are pretty damn difficult. But I don't mind it, because I have all the characters. I can play as whoever I want, whenever I want, and if I can dress them how I like, all the better.