That's not how I see it at all. I see it as a fight. You always have someone controlling the ring (in the center), and you have another hanging on the outside. Some fighters force others to be in whatever position they want their opponent to be in.
If you're comfortable dancing around the edge of the stage, so be it. Why do you bother letting go of the edge anyways? Stay on the edge and spam fireballs until time runs out.
However, if you're center stage underneath the platforms and not giving them an opportunity to attack effectively, how is that not controlling the game?
Hell, I'll turn your arguement around. You're on the edge and I'm spamming fireballs on your location, you have 2 options:
1) Pray you have projectiles to at least cancel mine
2) Try to get up and attack
Sounds like I'm pretty much in control.
As for the other reply, gimping abilities? Mario has better than average gimping abilities compared to some of the other cast, yet it counts for absolutely nothing in this game because every **** recovery is broken! Heck, any multi-jumper (MK, DDD, Kirby, Pit, etc.), and ROB have better gimping ability than Mario, to name a couple. It's too difficult to gimp in Brawl to make it worth investing all your effort into.
Skyler, the situation you describe means you are on the stage while your opponent is off. That's the ideal situation for any character in this game, because they're forced to recover and their options are obviously limited. That also means you're in control of the stage.
Basically, it comes down to this: If you're on the edge, you can use it to gain invincibility frames and stall for some time. Your opponent has no easy or direct way of attacking you. You can shoot some fireballs to keep them on their toes, however that's the only time you're really open for attack. You also have a chance to get your opponent off the edge with a throw, and rely on edgeguarding abilities to rack up damage or outright kill them.
However, it also means that you can't land any direct attacks at your opponent until you get up. If you get hit, it will hurt as they will be the ones edgeguarding you which may lead to a gimp as well. If you're losing, this is a very bad situation because you HAVE to get up, and it's pretty easy to hit someone getting up as the invincibility frames on the edge animations are very short and easily abused (the jump has none but you can attack fast out of it, but if they know you will jump you are seriously ****ed). They have plenty of ways to get you up when they want you to, via projectiles or purposely missing attacks to bait you into another.
Just to finalize my point, here's a vid of everyone's favorite Mario, Boss:
http://ca.youtube.com/watch?v=Rm5jKztiI-E
Notice how Boss always tries to get back to the middle of the stage, and when he's there he's firmly in control of the match? This is especially noticable from beginning to midway of the video. That's because the center of the stage is a critical area that you need to hold; you have great protection from the platforms, therefore it's harder for them to attack you and easier to attack them. Later on he's forced towards the edges and gets punished when he tries to get back in the center because the Marth read him (such as how CK baited Boss to roll inwards into a couple sword dances), which forced Boss back outside and left the Marth player in control.
This isn't even about spacing anymore. It's about controlling the stage, and learning what position you stand in and how to improve it.
Call me out if you think I know absolutely nothing about Mario, because I sure as hell know how to play this game.