The first series wasn't as good as the others, granted, but it did set a lot of stuff up, storywise. Sinclair's acting was bad, but in a funny way rather than a God-awful way. B5 just didn't work as well with the stand-alone episodic format, so once the main storyline got going it was much improved.
And compared to Star Trek? Much as I love the Trek and its cheesy dialogue, wooden arms-by-the-side acting, and tendency to resolve all problems in the last 5 minutes of the show with concentrated technobabble, it just doesn't come close to B5.
B5 definitely has its crap moments, but they are heavily outweighed by the good stuff. Riker incompetently firing one shot at a BoP and getting his ship destroyed, or Sheridan dive-bombing a ship full of nukes into Za'ha'dum, before throwing himself off a cliff because his balls are solid titanium?