very decent for your first
for your first sprite flash you did a good job.
here are some suggestions:
1)try and clean up your sprites a little bit. a little polish will go a long way
2)when mario would hit a block, it would bounce up and come back down but not land in the same place it was before. if you use rules you can be more precise when doing an animation like this... i had to learn that on my own : )
3) when mario was speaking, not only was it hard to read the text but it went too quickly. try using word bubbles and letting the text hang in the timeline for awhile so people can read what hes saying.
4)now that youve got your feet wet, try adding some good sound effects that gives it more of a Super Mario feeling.
i know this is a lot but you got potential for this. keep up the good work and i look forward to seeing more!