I'm surprised Firefly and Serenity haven't been mentioned, I found the character development pretty strong throughout the series, the overall plot was good and on an episode by episode basis the stories it told were well told and solid. The universe is compelling and I would have loved to see more within it, but really that ship has sailed now.

My absolute favourite sci-fi though would be The Matrix, this movie was just out at the time I was learning to program so it made all the stuff I was doing suddenly feel... cool. I love the universe as it's portrayed in the first movie, and I really enjoyed the Animatrix series as well. The second two movies..... I like, but I know most people are really unhappy with them, I don't think they hold up as well as the first movie did though.

Anime: Akira is great, but I would also suggest Space Brothers, it's a slice of life near-future where they're sending astronauts to the Moon again and relearning how to do it for the first time since the Apollo missions.

Cannot forget to mention the classics, Star Trek, Star Wars and Stargate. Oh and Futurama and Farscape. Man there's so much great scifi out there.