I always liked the theme song for The Greatest American Hero. It's kinda cheesey in that way only the late 70's/early 80's could be but it makes me feel optimistic. It was also a big part of my childhood along with the theme songs from Dukes of Hazzard and Knight Rider. Of course my favorite from that era is the A-Team, that one is actually the ringtone for my phone.
A bit before my time as I only learned about the show through late night reruns but I also really liked the theme song for Branded. That sense of honor and dignity in the face of injustice was inspiring.
More recently I would point to the theme from Firefly. It's a good song just by itself but it's also perfect at doing what a theme song should do. Tell the viewer what they're about to watch, in this case a space western, but without any clunky exposition that introduces the characters or premise. For as much as I used to love singing along with opening themes like Gilligan's Island, The Brady Bunch or The Beverly Hillbillies; I don't need to be reminded of the characters names and what the show is about at the start of Every. Single. Episode.