Since B5 Year One is considered by many here as a mere warm-up to the rest of the series, I present the following First Season entries as essential and fantastic Babylon 5 viewing. These episodes alone make the entire first year well worth the purchasing:
(Fear not: No spoilers here.)
DEATHWALKER: You'll love the sheer toughness of this one. A villain beyond understanding or redemption. Sinclair and Garibaldi willing to buck the system to do what's right. Sarah Douglas' electrifying portrayal of a character that even death is too good for. N'Toth at her wrench-swingin' best. Cool FX. The great twist and turns throughout leading up to an unexpected trump card played from an unexpected quarter. Riveting throughout.
MIND WAR: This was the first episode that many saw the series for what it was rather than "Well, it is doing right for what Next Gen is doing wrong." It was with this story that fans began to love B5 for ITSELF. Huge threat, huge stakes. A dynamite intro to the Psi Corps and Bester. (Giving us a new appreciation for Walter Koenig by revealing an acting ability that was NEVER properly spotlighted by Trek) A story that's awe-inspiring, imaginative, and intense. And, oh yeah...the sub plot about Katherine and Sigma 957 with G'Kar's speech capping the whole thing. "No one is what they appear to be" indeed. (And Psi Cop Kelsey is pretty darn cute too)
A VOICE IN THE WILDERNESS: This two-parter about the Great Machine is simply epic. Numerous factions dealing with a powerful and deadly discovery, the ticking clock, Sinclair's surprising willingness to oppose his own. The incredible FX, and two unlikely characters working together for the first time. Just delightful.
AND THE SKY FULL OF STARS: If you're a sucker for War Stories, here is all that and more. A great, intriguing payoff which raises as many questions as it answers (a B5 hallmark). Christopher Neame is a delightfully over-the-top heavy, the stylized FX has emotional impact as well as a cool factor, Chris Franke's chilling and sophisticated score, and of course there's the teeniest chance that the series from this point on is all in the mind.
BABYLON SQUARED: This one's an all-out rocket ride. Fully satisfying on it's own, this episode is also sequelized in a Third Season 2-parter. Here's a B5 that has it all, delivering what this series does best, action, intrigue, laughs (in the form of the could-have-been-annoying-but-was-great Zathras), high stakes, ect.
CHRYSALIS: Wow! Nothing was the same after this one. The best Season-ender SF had ever seen (Until B5 topped it in both Second and then Third years!). When watching this, you can feel the rug being pulled out from everyone's feet and the show take a decidedly dark and epic turn. The surprises and emotions keep hitting one after another until the end credits.
And perhaps the best Season One episode...
SIGNS AND PORTENTS: This brings home the idea that a true epic tale is being told. Not merely a series with strong threads of continuity, but clearly, Babylon 5 is a capitol "S" Story. Of course, stunning FX, music, and performances by regulars and guests alike, Morden's incredibly cool, creepy introduction, the Raider battle supreme, and Ladira's chilling vision of B5's possible fate.
Though, the above entries are essential viewing for the overall saga, Season One has some other very worthwhile episodes such as: BELIEVERS, LEGACIES, SOUL HUNTER, and, THE QUALITY OF MERCY.
Thanks for listening.