fox dominates almost everything. it's not a knock on the character, it's just that it's boring at this point that top 8 is usually fox/falcos. Last evo was good with variety, but i can't watch most weeklies because of it.
plus thats my brother's main and i fucking hate it.
Top 8s are not just Fox and Falco. Top 8 for SSBM has been very versatile at almost every major leading up to MLG/EVO. It just seems like there's a lot of Fox and Falco because some of the top players have one of them as a secondary and a lot of the A-tier players (like SFAT and Westballz) main one of them.
Let's look at a more recent major...
Get On My Level 2014 Top 8:
Mang0 (Fox/Falco)
Hungrybox (Jigglypuff)
Mew2king (Fox, Marth, Sheik)
Kirbykaze (Sheik)
Duck (Samus)
DJ Nintendo (Fox)
Weon-X (Fox)
I.B. (Marth)
And of course there are bound to be Top 8s with a lot of spacies -- it'll depend on the region but Top 8s definitely aren't dominated by space animals. I mean, MLG Anaheim had this as its Top 8...
Mang0 (Fox/Falco)
Armada (Peach/Young Link)
Mew2king (Sheik, Marth, Fox)
PPMD (Falco, Marth)
Leffen (Fox)
Axe (Pikachu)
Hax (Fox)
Hungrybox (Jigglypuff)
And then CEO 2014 had this:
Armada (Peach/Young Link)
Mang0 (Fox)
Hungrybox (Jigglypuff)
Mew2king (Marth/Sheik)
Plup (Samus)
Wizzrobe (Captain Falcon)
Fiction (Fox)
Colbol (Fox)
There is character variance in SSBM's top 8 for tournaments. This isn't me targeting you specifically, this is me making it so everyone knows this because I see it brought up a lot. Weeklies largely depend on the region as far as character variance goes. Something like Super Smash Sundays is bound to have a lot of spacies because it's the west coast, WC has most of the A-tier players that use a space animal. Meanwhile something like Smash @ Xanadu won't have as much space animal density, instead you're likely to see some more variance from players like ChuDat (who uses ICs) to Husband (who uses Marth) to Boss (who uses Mario, Luigi, Doc) to DP (who uses Falco and apparently used to live on the west coast, surprise surprise...) and so on.
As for Fox dominating everything (I assume you mean him winning overall), it is mostly because of the person playing him (Mang0) who is very consistent with the character. He's taken him to a level most other people can only dream to take the character. It used to be impossible for Fox to win a major overall because of how much the person playing him had to be consistent but nowadays Mang0 has been extremely consistent. The only majors he let slip out of his hands was SKTAR 3, Super SWEET, and CEO 2014. PPMD won SKTAR 3 with Falco and Marth and Armada won Super SWEET with Peach and Armada won CEO again with Peach. Consistency is super important in Melee and is what makes it so interesting to watch because you have no idea how good someone is on a given day.