Ryan McAvoy said:

DuracellEnergizer said:

The overuse of human and rubber forehead aliens.

This says it all ^.

When the show got so complacent that it would introduce us to new Alien races week after week with ever so slightly different nose jobs, was when the problems started.

Then when it got to DS9 they thought it was exceptable to have the main Alien race (The Bajorans) that the entire show revolved around, have four nose ridges and an earing?! When you had Babylon 5 airing at the same time who had wierd and freaky aliens (with peacock hair, ornate bones growing out of their heads, full reptillian facial appliances or no physical presence at all) then your franchise starts to look tired.

To be 100% fair The Bajorans were a hold over from TNG and they were made that way so they would contrast with the more inhuman Cardasians who were lizard people and didn't look all that human for TV aliens and lived in places that didn't look very human at all.

I will agree that B5 was better written and had better aliens but I think both TNG and Ds9 were great series that stand on their own. I was just rewatching the third season of TNG on bluray for the first time in years and I was expecting it to be really dated but I have been surprised to find that most of the episodes hold up pretty well.