The greatest Flash game of its time, but...
...it definitely shows its age. I have very fond memories of the original Pico, and playing it again is certainly a joy. But Flash technology has improved since this game was made, as have Flash artists. The 4.52 score that this game has at this writing would put it at #1 all-time on the Portal, and I don't think it deserves that. There have been much better games made since then, both by Tom Fulp himself and by other artists.
But you do have to give it credit--Pico, along with Assassin, was hugely popular in Newgrounds' earlier days, and it helped bring about the transformation of Newgrounds from a site for Tom Fulp's personal things (Flash and otherwise) into the huge community of Flash artists that it is today. Newgrounds would not be what it is today without it.