Very nice! The only problems here are graphical and minor things.
You had some buggy graphics, such as here.
You had cutoff several times in the level, such as here.
Surprisingly, there wasn't much clash in the main area. Here, however, is a different story.
The Zelda 2 backgrounds clashed, and the SMW Ghost House graphics didn't fit in well with the SMB1 based level.
This doesn't look right. Here's how you fix it:
That still clashes, though. Also, why are several NPCs and the starting points in the air? Put them on the ground, so it looks
slightly more professional.
You also shouldn't put one-block-high areas, such as here.
Also, you put SMB3 items in blocks in an SMB1 world. If you scroll through long enough in the possible contents of the box, you will find SMB1 and SMW items.
Please, put multiple powerups, or at least don't put Mushrooms in several blocks.
While it didn't look the best, this played very well, and I enjoyed it!
This should go in Pretty Good,
maybe a really high Average.