What are some good examples of SMB-styled levels/episodes?

[_____X_____]

Like the level "Retro Town" in The Insavion 2.

[HeroLinik]

Like the level "Retro Town" in The Insavion 2.

Retro Town is in The Princess Cliche, not The Invasion 2. The level you're referring to here is Retroville.
It's not that easy finding SMB1-styled levels/episodes to be honest because it's a rather unconventional style, but to start you off, try this one.

[bossedit8]

Here's another example:



Original link: http://www.youtube.com/watch?v=0CMYroDtN8U

[h2643]

You can try to play Mario Forever X, it's a nice SMB1 styled game.