I watched Smallville religiously back when it was on the air. I also watch the Flash. I love both shows and both have their good points and their bad points. I will tell you this both shows are about equal in terms of special effects. There some special effects where I'm going "OMG that was aweful" other times there special effects where I'm going "OMG that was awesome." They both have their ups and downs.
If you ask me Season 5-7 where smallville weakest seasons. The whole Lana, Lex, Clark thing got annoying. I was glad when Kristin Kreuk left the show. By season 7 the show seem to be less about Clark and more about every one else. Season 8 things got back on track and the show became great again. Now don't get me wrong there where still some great episodes between season 5-7. One my favorit when Clark crash Lex and Lana Dinner rehearsal. Was so much fun watching him go off on every one. It was always awesome when you see Tom go off like that. It becomes very scary in good way.
I also agree that Iris has become a weak part of the show. I would be okay if they killed her off. She has always been a very bland character unfortunately. However I still love the show and story are really good.