Most people don't like Jigglypuff as it has 'non attackive' super moves
But it depends on how you play
Olimar
It depends on your skills. I'm the worst with Jigglypuf.
ash and his Pokemon
No, Pichu is not a playable character in Super Smash Bros Brawl
Shadow is not a character in Super Smash Bros Brawl, unfortunately.
Midna is not a playable character in Super Smash Bros Brawl
What character?
No, Jack Skellington is not a playable character in Super Smash Bros. Brawl.
Dark super Sonic is not a character in Super Smash Bros Brawl.
mewtwo is not in super smash bros. brawl however mew is a trophy character
Groudon is in Super Smash Bros. Brawl as a Poke Ballsummon, but not as a playable character.
There is not playable character called Jet in Super Smash Bros Brawl.