Flash

The Flash is definitely one of the best of the Arrowverse. It does feel a little boring and repetitive at times, but the characters are really likeable. Another I'd recommend from Arrowverse is definitely Supergirl. Has a similar vibe to The Flash out of the rest of the Arrowverse lineup. CW also recently came out with Stargirl which was pretty good. A different tone from The Flash, but in a good way.