ferbus will NEVER be dethroned!

Depends what you're looking for in a series. Do you want something with a good amount of comedy? Then go watch Den-O, Double, or maybe OOO. Something more serious/dramatic? Try out Kabuto or Blade.

I would say its difficult to decide where to start. Heisei shows, many say Decade, but I would warn that show contains a number of big spoilers. I wouldn't say W, because I think you might be disappointed with whatever you watch next. Fourze is ongoing atm, so you'll com in live, but its so far not hugely representative of how the previous Heisei shows were done. I honestly think start with Kuuga and work your way forward.

Showa, original series is the best bet. Black's out there as well, but thats really a proto-heisei.

I actually started with Ryuki then watched ZX. I'm at the 1st episodes of Ryuki and dig it so far. I want to watch V1 and W, and Kuuga/Kabuto/Blade sound good from what you guys said.

Any of them. Just pick one. Flip a 20 sided coin. They're all good.