Basically, whatever looks fun to you probably will be.

Pretty much every Rider show out there has weaknesses and strengths, so there's no real magic bullet here.

That being said, Agito comes to mind a being a very balanced show, but it's not like the others aren't worth your time.

W, Ryuki (you also kind have to watch the movie if you want to see the final 2 riders), OOO,Kiva, Decade, and Hibiki.

For getting back into the show, I wouldn't recommend Decade. Decade is a show that you either love or hate, so to be on the safe side, I'd say it's better to watch some other Heisei rider before.

I'd say just find a show with a premise/designs you like and go straight in.

So i watched W and loved it i tried watching Fourze again i don't know if it is the high school theme, or the just how annoying the lead character is but i can not get into it (sorry Kickback) I'm going to try OOO next.

A dose of W, Kuuga, Den-O, Ryuki, and Fourze.

Ryuki, W and do try to keep up with Gaim because Gaim is slowly turning into my favorite season.