spectacular spiderman is very good, current, and def geared towards the younger boy crowd (making assumption on age since you said "young nephew"). i think season 2 just finished airing in the US on some channel or other (aired much earlier in canada).. so either season should be 'around' Having said that, if your nephew is a "spiderman purist" (knows all the comic books, etc) he might not like it only because they take a couple minor villains and "spin" them with something a little different (i.e. the identity of one/two particular minor villains were changed, etc); it's done transparently and it's good as it keeps even the hardcore fans guessing. but if he obsesses over details like that then it may annoy him...
I was also a big fan of the spiderman animated series from the 90s. However, that series is better as a whole rather than bits and pieces from a small dvd set.
spiderman and his amazing friends (70s?) was good for its time but definately won't hold the attention (animation wise) of a kid these days.
think there was also a spiderman unlimited in the late 90s. but, it was basically alien world spiderman. i didn't like the change of setting so i didn't watch it and can't say that i was able to get as far as even giving it as a chance (spiderman is supposed to be about 'every man put in a unique situation, but this was way too out there to hold on to that 'everyman' roots)
there was also a computer animated spiderman series done by MTV (neil patrick harris as one of the voices, etc). It didn't get more than 8 episodes (something like that). while it was sort of fun, i don't think it was necessarily "dvd ownership" worthy.
anyway, bottom line, out of all the spiderman series i know of, the most recent "Spectacular Spiderman" seems like a good fit for your young nephew.