I still find complaints about TNG's first season rather strange, the ratings were high and they won a Peabody Award for The Big Goodbye. If anything their problems seem to come from trying to make an emsemble series and the series worked better after they lost Tasha Yar. The first season of TNG also suffered from a ravolving door of writers.
Still just I'd stated in the Stargate forum even B5 needed more than one season to really get started.
Staying on topic though In The Beginning can stand by itself, it was after all the movie of the week so to speak and plenty of people saw it without prior knowledge of the series. It works better in conjuction with the series but for the most part it works just fine on it's own.