I rank Babylon 5 up there with The Wire, Neon Genesis Evangelion and I, Claudius as TV storytelling at its peak. It also kicks arse from the start, only messing up slightly in its final season. The Gathering is slightly clunky but it's trying to do somethign brave and different in a way that none of the modern Trek pilots do. Michael O'Hare as Sinclair is my favourite main B5 character so I find myself rewatching S1 a lot more than S5. Hell, I'd take him over any of the Trek captains.
Don't start with In The Beginning. Ruins the entire mystery of Season 1. Boot up The Gathering and let the story unfold.