It's not in the same optimistic genre as Star Trek TNG, but the 100 is watchable. It has a younger cast, so it might be better at getting younger viewers into sci-fi. Other current sci-fi, also not in the TNG genre but still enjoyable: Continuum, Defiance.
Actually it's a great premise, but it is overshadowed by the "cool teen" factor which plagues other shows on the CW (though Arrow has mostly been able to escape that..for now).
The Vampire Diaries is a good example of what being on the CW does to a show. It started out in the first two seasons as a dark, violent, mostly serious take on the "teenage vampire" trope, and could be enjoyed by both teens and GenX/GenY fans of the vampire genre. It has a pretty good cast (Nina Dobrev's "Katie Holmes v2" notwithstanding). After those first seasons, however, it devolved into the stereotypical teen drama + nonsensical mysticism. Eventually, after seeing a school dance or town festival as the main plot device every two episodes, I had to stop watching it. My wife still watches, but she tends to enjoy the occasional plotless teen drama.