I do a league and some rivalries came up naturally because of match-ups in the Smash league play. I divided the Smash Characters into conferences starting with Melee and continuing into Brawl. Certain conferences have changed over time as have characters affiliations to them. Also some of the Melee characters were too important to remove so I listed them as recolored version of characters in Brawl. As it stands now there are 5 Conferences and no independents
Mushroom Kingdom Conference
Mario (original member all 74 seasons)
Luigi (original member)
Peach (original member)
Bowser (original member)
Dr. Mario (original member, recolor of Mario since move to Brawl)
Yoshi (original member)
Donkey Kong (original member)
Wario (joined when getting Brawl)
Diddy (joined when getting Brawl)
They all play each other every season but the huge rivalries are Mario vs. Luigi, Mario vs. Sonic (OOC rivalry), Luigi vs. Fox (OOC rivalry), Peach vs. Samus (OOC rivalry), Peach vs. Zelda (OOC rivalry), Yoshi vs. Donkey Kong, Mario vs. everyone basically lol, Luigi vs. Peach, DK vs. Diddy. Mario vs. Link is also huge because they are historically the two strongest programs all-time.
Mushroom at the moment plays 8 Conference games and 3 OOC games. They are usually the strongest Conference although historically the Hyrule conference ruled until the late Melee era.
Hyrule Conference
Link (original member)
Ganon (original member)
Zelda (original member)
Y. Link (joined season 2 after unlocked him on Melee; still call him Young Link but use Toon Link on Brawl).
Ice Climbers ( joined season 2-3 from Indy and has went Indy again only to rejoin)
Marth (original member)
Roy\Ike (original member after expansion of Brawl Ike took on his legacy and history)
Pit ( joined 3 seasons into Brawl era after Indy)
Past Members: Kirby was in the league 3 seasons
Rivalries: Link vs. Kirby (OOC), Link vs. Ganon, Ganon vs. Ice Climbers, YL vs. Link, YL vs. Zelda, Link vs. Marth, Marth vs. Roy/Ike, Ganon vs. Captain Falcon (OOC), Zelda vs. Peach (OOC), Zelda vs. Samus (OOC), Zelda vs. Jigglypuff (OOC), Ice Climbers vs. Kirby (OOC - first two Independents). Hyrule is top heavy these days with Ganon, YL, Link, and Marth being the powerhouses of the league while the others are far weaker members but have had success at times. Nobody outside of the Big 4 (Link, Ganon, Young Link, Marth) has won a Championship.
This league plays 7 Conference games and 4 Out of Conference games each season. Historically very successful but top heavy, doesn't have the balance of Mushroom Kingdom Conference.
Space Conference:
Fox (original member)
Falco (original member)
Ness (original member)
Samus (original member)
Captain Falcon (original member)
Olimar (member since Brawl move)
ROB (member since Brawl move)
Wolf (member since Brawl move)
Lucas (member since Brawl move)
Past Members: Mr Game & Watch (until Brawl move), Kirby, Pikachu, Jigglypuff (last three joined for a spell in late Melee era).
Rivalries: Fox vs. Falco, Fox vs. Luigi (OOC), Fox vs. Wolf, Olimar vs. Fox, Falco vs. Wolf, Ness vs. Samus, Samus vs. Peach (OOC), Samus vs. Zelda (OOC), Fox vs. Link (OOC), Mr. Game & Watch vs. Ness (OOC), Ness vs. Lucas, ROB vs. Olimar, Captain Falcon vs. Ganon (OOC), Captain Falcon vs. Samus.
Nobody likes Fox in this league as Fox has dominated this league. Falco is the second most powerful program so that match-up in the final week as a rivalry game is always huge. Olimar in the middle and late Brawl era has come on as a tough program, especially at Olimar. Captain Falcon and Samus never seem to be able to get things going although Captain Falcon has won a Championship. Wolf is another program that is hyped but falls a part a lot.
This league plays 8 Conference games and 3 out of conference games a year. Traditionally dominated by Fox with Falco, Captain Falcon, and Olimar having runs for a time. Falco, Captain Falcon, and Wolf all have championships although Falco is the only one with more than one.
Pokemon Conference (this conference formed in Melee era and collapsed because Pikachu ran it and wanted more competition so went to Space with Jiggs, reformed in Brawl era and has been more successful):
Pikachu
Jigglypuff
Mewtwo (recolored Lucario)
Lucario
Charizard
Squirtle
Ivysaur
Past Members: Pokemon Trainer (Char, Ivy, and Squirtle were one char in 1st season of Brawl era), Pichu
Rivalries: Pikachu vs. Mewtwo, Mewtwo vs. Lucario, Lucario vs. Sonic (OOC), Char vs. Ike (OOC), Pikachu vs. Squirtle (great historical matchups but Squirtle has been weak lately).
League has been dominated by Pikachu historically but in Brawl era has seen success by other teams. Only two Championships all-time from this league and both in Brawl era with Pikachu winning one and Mewtwo winning the other. League has been far more competitive in Brawl era but seen as the weakest league.
This league plays Six Conference Games and Five out of Conference games
Dreamland Conference (only formed in Brawl era):
Kirby (original member)
King Dedede (original member)
Metaknight (original member)
Mr. Game & Watch (original member)
Sonic (joined middle of Brawl era)
Snake (joined middle of Brawl era)
Shadow (recolored Sonic, formed a team middle of Brawl era as member of league)
Rivalries: Sonic vs. Mario (OOC), Sonic vs. Lucario (OOC), Sonic vs. Snake, Sonic vs. Kirby, Kirby vs. Snake, Snake vs. Olimar (OOC), Kirby vs. Ice Climbers (OOC), Kirby vs. Pikachu (OOC), Kirby vs. Link (OOC), Kirby vs. Mario (OOC), Mr Game & Watch vs. Ness (OOC), Meta-Dedede-Kirby all consider each other rivals, Sonic vs. Shadow
This league is new and up until its expansion, totally dominated by Kirby. Sonic joined at its height and enter period of decline but still been powerful. After several seasons in Snake began to rise to prominance. League dominated by Snake, Sonic, and Kirby. Other teams have had some success but King Dedede and Metaknight are among two of the worse programs most seasons.
This league plays 6 conference games and 5 non conference games.
League is on 74 seasons. End of season is a Tournament of 16 teams seeded based on performance during season. It is a single elimination and all Conference Champions are automatically allowed in with the rest being at-large births. Higher seed has home course until Final Four. Final Four is at neutral Brawl Battlefield. Team success is keep up by Conference Championships, Final Fours, and overall Championships. Historically Mario and Link most successful while Sonic and Fox have beem most successful in Brawl era (with Mario coming close in this era as well). Ganon, Donkey Kong, Dr. Mario, Kirby, Marth, Y. Link, Peach, and Luigi are also significant powers.