I sure hope Sakurai is never allowed near the Smash Brothers series ever again, it is clear his vision with it has changed over the eight years since its inception. I hope we do see another Smash game soon because the last game was nowhere near what I wanted. Personally I'd love a Smash game involving just Mario characters as there are tons who I'd love to take into the ring (or onto the floating platform I guess).
I don't think I had unrealistic expectations for Brawl. In fact, before its release I deliberately tried to avoid any information regarding it so I wouldn't over hype myself for it. The biggest difference I see in Melee and Brawl is that Melee felt like a tribute to Nintendo whilst Brawl feels like an advertisement for Nintendo. Rather than express what I wanted, I'm going to list what I didn't want:
-An expanded single player mode. Smash is a party/multiplayer game, and while things like Break the Targets and Multi-Man Melee are fun, I'd gladly trade them all for a few extra characters and stages.
-Dumbed-down gameplay. Smash is already a pretty simple game, there was no need to alter any part of it. No -L-cancel, no hit stun, infinite air dodges, too many powerful moves... oh and what is up with the random tripping? This game is random enough, no more of those elements are needed.
-A more serious art style and tone. This is a game where Nintendo worlds collide, most of which are pretty vibrant I might add. Don't try to create a story to explain how it happened, just let the insanity ensue.
-Contrived stages. Almost every stage in Brawl has some sort of hazard, such as wandering enemies, moving sections, or some other nonsense to interfere with everyone. There are very few traditional stages with no frills, and some of the ones which were included are too small. The Stage Builder is a way to create more traditional stages, but it is extremely limited and very bland visually; I'd gladly trade it for some premade stages that are actually well-designed.
-Too many powerful items. Lots of them are one-hit KOs or can KO at low damages. And I couldn't loathe the Smash Ball anymore than I currently do.
-Trophies and stickers. The trophy feature in Melee was interesting but I'd still have preferred that effort spent on more characters and stages. Brawl adds stickers to the mix of useless content, and almost all of the trophies and stickers don't go back farther than the GameCube era.
-No more unique stages for Break The Targets. They've been replaced by five uninspired levels that aren't designed around any character's specific strengths and weaknesses. The single-player adventure has this problem as well.
-Over half the music being ripped straight from the originals or original compositions created for the game. The original music doesn't fit the game at all.
-Masterpieces. What a waste of disc space, and a shameful attempt to sell VC games.
-No Toad and Birdo. Okay, now that's all me I know, but still...
-No third-party characters. I'm probably alone on this (and in disliking Brawl in general), but Smash is for Nintendo characters ONLY. At least Snake got his start on the NES, but Sonic is all wrong.
All of that is even before I get into what I did want to see, but this post is getting ridiculous as it is.
Basically, it isn't that Brawl didn't have enough content, it is that it went in a different direction than the things I wanted to see in a sequel.