As much as I enjoy the original show I find that the longer Stargate has gone on the more it has missed oppourtunites for some really great stories, the Asgard are one good example, they came into the show very strong and with each season they seemed to get weaker and then be written out of the show all together, they were used but not as much or as well as they could have been, in my opinion.
The ascended ancients were not used much either because they wouldn't involve themselves in human struggles, and then the Ori were just too much like the Goa'uld to be enjoyable, ascended beings using religion to enslave, it was basically the same storyline as before, with the SGC trying to incite rebellion and independence so I couldn't enjoy it very much.