This is what I'm talking about. You're trying to compare the first couple of worlds to the entirety of games you already played for over a decade and a half. All Mario games build up the complexity and challenge as they go. The first levels usually aren't going to stack up when you're remembering stuff from late in the other games.
When does NSMBWii and NSMBU get good? Well, if we're comparing to the older Mario games, immediately. As far as 2D Mario goes, NSMBWii and NSMBU have some of the best opening worlds. Here is every level in SMW:
http://www.mariomayhem.com/downloads/mario_game_maps/super_mario_world_levels.php. Look at the first few worlds. The levels there are pretty plain and empty. None of that is better than what NSMBU does. NSMBU's levels are huge yet densely packed and brimming with ideas at every turn. When does SMW get good if NSMBU's levels are boring?
There unfortunately are not maps for NSMBWii or NSMBU, except for this one I made myself of 1-1 in NSMBU for another thread:
http://i.imgur.com/PJCZDo2.jpg for a comparison of level lengths across games:
http://i.imgur.com/cW7LbdP.jpg. I can describe the levels though for the sake of comparison:
1-1 Acorn Plains Way: A plain level (pun intended) to introduce the super acorn. Designed with speedrunning non-stop in mind.
1-2 Tilted Tunnel: An underground level featuring giant crystal platforms that move when you interact with them. Contains a secret exit that takes you to 1-Blooper and World 5.
1-Tower: Crushing-Cogs Tower: First tower of the game. Have to navigate giant spinning cogs.
1-3: Yoshi Hill: Yoshi introduction level. Monty moles on spinning hills and cliffs.
1-4: Mushroom Heights: Simple mushroom level to introduce balloon baby yoshi.
1-5: Rise of the Piranha Plants: Level filled with tons of piranha plants of various sizes on moving platforms.
1-Castle: Lemmy's Swingback Castle: Most of the floor is lava and most of the platforms are swinging like pendulums.
1-Blooper: Blooper's Secret Lair: An underwater level set in a cave filled with pipes shooting current that move and bloopers.
2-1: Stone-eye Zone: Moai-like stone heads move up and down and fall in various ways in a desert level with quicksand and sand geysers. Designed for speedruns.
2-2: Perilous Pokey Cave: Cave level filled with pokeys all over the place with quicksand and sand geysers. Second part of the level is pitch black and filled with pokeys and swoopers.
2-3: Fire Snake Cavern: A pitch black cave filled with fire bros and fire snakes that makes good use of dynamic lighting. Features glowing baby yoshi to light your way and stun enemies.
2-Tower: Stoneslide Tower: You have to spin on top of cranks to move stone platforms and other elements.
2-4: Spike's Spouting Sands: Spikes (the enemy) roll spiked balls along the ground. They travel up and down hills and are pushed into the air by sand geysers and are affected by gravity. Secret exit to Piranha Plants on Ice and World 5.
2-5: Dry Desert Mushrooms: Spikes (the enemy) toss their spiked balls straight down from above as you ride moving platforms and navigate shrinking/expanding mushrooms.
2-6: Blooming Lakitus: Lakitu tosses seeds that grow into piranha plants wherever they land. Most of the ground is moving so the piranha plants move along with it.
2-Castle: Morton's Compactor Castle: Lava-filled castle where most of the platforms are giant blocks that move in and out to crush you.
2-Ice: Piranha Plants on Ice: An ice level featuring a ton of venus fire traps and small ice platforms that melt when hit by fire, causing giant ice blocks they support to fall.
I made screen caps for every level for a previous thread:
World 1:
World 2:
World 3:
World 4:
World 5:
World 6:
World 7:
World 8:
One of the things I love about NSMB in general is that every level has a very unique identity that sets it apart from every other level. It keeps things fresh and makes the levels more memorable. SMB3 was like that, too. Just looking at the images above there are so many levels I have very fond memories of. It's the pinnacle of EAD's 2D Mario creativity and craftsmanship.
Anyway, I'm very much looking forward to this. Easily my most anticipated title this year. I can't wait to make levels.