Even though he has only made one true appearance, my personal favorite has to be Count Bleck from Super Paper Mario.

Nearly every villain in the Mario universe has a character as flat as a piece of paper, pun very much intended, as they are pretty much just generically evil with no other real traits.

Count Bleck, however, has complex motives, a dynamic character, and a really cool cape a misunderstood quality about him that blurs the line between good and evil.

The Mario series really needs more characters like him, in my opinion.

I kinda have to agree with Q, I really liked Count Bleck from Super Paper Mario even if he's only been in one game. He's still awesome. He's a pretty deep character from someone as flat as paper.

Heck, I couldn't even tell what the heck he was really up to my first time playing through the game.

I liked Bowser Jr.

He was a new character that just did everything that he did for the lawlz.

That's respectable, because that's mainly why I do everything I do.

Kids will be kids.

Luigi has always been my favorite Mario character. I usually felt that he was the underrated brother.

Yoshi, for 20 years, no one even celebrated yoshis 20th anniversary? Yoshi actually talks, in the super Mario world show, super Mario 64, then super Mario galaxy 2! Really funny moments in Mario galaxy 2 just wanna make you laugh.

My favorite character is Iggy Koopa (that's why I'm called iggykoopa), he's one of bowser's other sons

oh god here we go time to list all my favourite new characters from Mario: Toadette, Rosalina, Baby Daisy, Count Bleck, Baby Peach, Birdo and Lubba :3

I liked Bowser Jr. An little evil version of his dad. Who knows what he'll grow into in the future.

My faviorte has to be petey piranha the way she is a walking flower seem like a cool thing nintendo has made.

I like bowser jr a lot he's like the only person i play with besides toad, they both are very interesting characters.

I have to pick the giant Goomba from New Super Mario Bros. Wii. He was a boss and he looked so cool.

Well, Waluigi is certainly the most underrated character in my opinion, but I'm not sure that he's my favorite of the newer ones. After all, the Paper Mario games have a lot of awesome party members. I'll go with him for now, though.

My choice? It would have to be Funky Kong.

I split my favourites into NPCs, playable characters, items (because they're mostly happy dancing plants), and villains.

For NPCs, I'd have to say the Lumas. They eat, turn into features, items and transport, and in the first game they sacrificed themselves to attack, pretty much, an undead form of one of their own kind.

For a playable character, I'd say Rosalina (I knew she was playable in like 2 games so that's why I was able to put Lumas for NPCs). The way I'd have to describe her voice is quite mature for a forum that isn't marked 13+. What I can say is, she kind of personifies the beauty of the night sky. And to look at her with stars in the background just makes my heart beat so hard that it touches my ribcage and causes excruciating pain for me.
...she would also be quite useful in an RPG. Using an artificial gravity field would build up her physical strength without altering her body on the outside, especially using an external surface on the observatory which will expose her to the cold emptiness of space, and she has access to powerful magic and has a shield that doesn't even look like she consciously puts it up (as seen whenever you jump on her). With how simple but complex her starship is at the same time, it seems to be really powerful on its own considering Prima's guide for the first SMG states that she had used the Comet Observatory to distract Bowser's airship armada. (Although, Prima is very often incorrect.)

For items, I'd say the Rock Mushroom is my favourite. I want to see an updated pinball game, or maybe a boulder form battle with Rock Mario from SMG2 and Boulder Bowser from the first game.

My favourite villain, and possibly my favourite of my favourites (aside from Rosalina) is Bowser Jr. I think it's great that he finally breathes fire in New Super Mario Bros. Wii.
If he replaced Bowser in the original Super Mario Bros., he would paint enemies to help him on the bridge, with the enemies painted being different in each fight. In an 8-4 styled battle, he'd have 4 or 5 Hammer Bros. with him. I don't know.
If he used Bowser's Super Mario Bros. 3 style, he would have to call his Koopaling Klown Kar to do that slam attack from New Super Mario Bros. U. Then he would hop out of it when the blocks are destroyed. Then, because he would fly out of the gap when a whole column is destroyed, you would wait until he hopped out of the Klown Kar again, and then knock him into the pit with koopa shells. ...or, you can jump on him right when he jumps over the gap.
I think he would very easily imitate the Super Mario World fight, except his Mecha-Koopa throwing would be more difficult to dodge because of him throwing both on the same side (i.e., directly at Mario). To bring out a Big Steely (the massive ball that rolls along the stage in the second phase) he would have to paint it due to its size. Finally, the slamming attack in the third phase is faster and more accurate than Bowser's. The fire rain transition between each phase would be smaller but the fireballs would home in just like in his fights in New Super Mario Bros. Wii.
If you wanted to put him in the place of Mario64's Bowser, he would have to have Blue-Breath Bowser Statues around the arena between the Bomb Orbs due to his inability to breathe an actual stream of flame.

...I think that's all I have to say on the matter.

My favorite Mario character, after Super Mario 64? I want to say Bowser jr but he was in at least one snes game. If the newer toads count, then them deffinitely. If not, dry bones, since it comes down to dry bones and Waluigi since they're the only ones I know after that, excluding the mario golf characters.

Yoshi is my favorite character from Mario, but he was introduced in Super Mario World, so...
My favorite character after Super Mario 64?

Hm, lemme see... I actually have 2 favorite characters that aren't in the main series.

1: Goombella. Oh, my god, when I first played Paper Mario: The Thousand Year Door, and I saw her attitude in the 1st Ms. Mowz scene, I was like "OH NO SHE DIDN'T!". I was in Grade 1 at the time, so I didn't say anything inappropriate, but I'm like, mhm, she's not afraid to tell someone about themselves. Calling Ms. Mowz a total floozy... that thing is stuck in my head for the rest of my life. Gameplay wise, I liked Jumping as Mario since it did good damage after Power boosting badges, and she does some good damage too. Multibonk is awesome, so is Rally Wink. ;p

2: Vivian. I felt so bad for her. She was always getting yelled at for no reason, and it kind of reminds me of myself since we're both the youngest of my family and we both have to deal with being nagged by the "superior" ones. (I'm a male though :p)
She was also pretty original; I always wanted like another ghost like character in Mario that's not a Boo and her speciality is fire, which was unique for a ghost like character. Also, I loved that hat for some reason and she's pretty cute.
Gameplay wise, her Shade Fist is good, and Fiery Jinx is amazing. That move pierced through defense and set all enemies on fire (as long as they weren't immune to it lol). While that move cost a whopping 6 FP, 2 Flower Saver Ps lowered that to 4 so I could abuse that move more. She snaps her fingers, everyone catches on fire. Now everytime I see that move, I'm like: she just became Ms. B**** in there, yesss! Veil also came in VERY handy for the final boss. I will gladly dodge a 15 damage attack (or however much it does LOL) for the cost of 1 FP and Mario's turn.

So, yeah, I love my Goombella and my Vivian. XD

Luigi is in my opinion the best since Mario gets all the spotlight of course that's because Luigi isn't the fighting type but still Luigi is awesome and his Luigi mansion games were so fun to play Luigi deserves more games where he is the hero of the game go Luigi!