In the first season The Flash is easily one of the best superhero shows I've ever seen. Every single episode drives the overall season-spanning story arc forward. And the show moves along at a really good pace within each episode as well. Pacing is super important to me. When shows get too slow I get bored, tune out, and give up on them. That didn't happen at all throughout the first season of this show.
It even ended on a cliffhanger that makes me really want to jump into season 2 immediately. So, I probably will.
One of the coolest things about The Flash is how much fun Barry Allen has being The Flash. It's not some grimdark angsty superhero like so often happens. From the very first episode Barry thinks his powers are awesome. He has fun with them while training and while saving people. You can really tell that he loves being the Flash.
It doesn't hurt that this show mixes in science, pseudo-science, time travel, and a bunch of other stuff I love.
DC Comics and superheroes have never really clicked with me, so I'm as surprised as anyone that The Flash is one of the best shows I've watched in the past few years.