Main character guy has ridiculously low contrast, you might wanna up it if you want him to look like anything but a dark silhouette.
Background sky wants either more colours or a more colourless foreground - right now the gameboyish simplicity clashes a bit with the foreground. ..
Buuut I'd say introduce more highlights to the picture, keep the sillhouetteness of the background but add more colours, make some transitions smoother and - at all costs, avoid single pixel noise, like what you've got going on at the lamp posts, it hurts my soul - more colours, smoother, spread the highlights out more, right now they really stick out a lot.
Yeeah well I think you should aim for large clusters of colour, a fair amount of buffer colours but not too much AA, but crisp pixels and solid shapes and sillhouettes ... Gah
I don't know! First of all try introducing some highlights into the foreground and up the contrast in that general area!
Edit: Also generally good stuff - pixel tech might be a bit rusty but your construction skills are awesome - and those are important! So good luck and please do continue making this, it's awesome.