Watched the first season of Flash and it was fun, but gave up halfway in the second season, too repetitive and not enough progress.
I loved Arrow for a while, but after season 2 or 3 it just began to be sometimes ridiculous and full of plot holes (for example, anyone with a few days of boxing training can kill the best killers in the world easily...). I dropped it after a few episodes in the season 4.
I need to watch Gotham though.