It's a good start I think. There are some anatomy problems, mostly in his lower half. His right leg looks odd as if from the knee down he's missing part of his leg. This comes from the positioning of the foot and the fact you can't see the lower part of his leg.
Personally I find the background colour rather distracting. Whether it's the colours or all the blending going on I'm not sure. It could also be that it's takes up so much and goes right over the buildings in the background. The perspective needs some work back there as well. Even if it's forced it should give the idea of a vanishing point and with building as the largest part I can see the lines delineating the windows simple run parallel with each other. The other buildings don't follow the same vanishing point either. Which to me isn't generally a big deal but one seems to be one point perspective. The one building in the foreground is more finished than the others as well which can take the focus from Spidey. I would suggest treating all the buildings the same way. Either make them all simple outlines or work them to same degree.
I like the composition. Spidey is large and clearly the focus. The action and gesture of Spidey is thought out and he doesn't look to posed. Good use of lines to lead the eye to Spidey, the perspective on his webbing, the lines in the buildings.