Both Decade & OOO start off pretty strong imo, but I think W & Fourze got pregressively better while Decade (and to a lesser extent, OOO) got a bit weaker in the middle. OOO made up for it in the final arc that really propelled the show, but Decade never really become a great show (although that two-parter with Black & RX were terrific). If I were you, I'd pick W to see first, then either OOO or Fourze. You can skip Decade if you want to.

Just finshed up the W vs decade movie. I love W so much more now, but decade is growing on me.

The wife and I watched Den-O The Final Countdown tonight. I liked it. Skull and Hijack forms were good, need a figure of them.
I'd say I'm sad to see the characters go, since supposedly this was Farewell to Den-O and the Gang, but they clearly come back, so I look forward to their next adventure.

Well at the time it was an actual farewell, it was all that was planned. The reason Takeru Satou doesn't play Ryutaro in the Decade crossover movie is because they never originally planned to do more Den-O (and he's never returned since because of his involvement playing Kenshin Himura). But the popularity was clear for that franchise so they had to do more. They shoe-horn in that whole "the timeline has been changed" nonsense so that they can use the kid who played young Ryutaro from Ore Tanjou. Still a good movie but Final Countdown was easily the peak of the Den-O franchise. The final fight that includes all the Taros in their Den-O forms with Zeronos taking on all the baddies was just ridiculously epic.

It sure was.

So...I just finished OOO. And I started a week ago. That was such a great show. I'm not sure what people mean by the middle not being so great. I thoroughly enjoyed it.

I'm still watching an episode or two of Ryuki every couple of weeks, and for the fun of it I started Kabuto the other day. Seen 3 episodes so far, and it's engaging, so far.

I really enjoyed OOO alot. I felt it had a weaker start and to some extent a weaker ending but I've always felt the middle was strong. The ending only loses itself because I don't think the writers knew what to do with the Greed once Maki became Kyoryu. Everytime I see Eiji in an episode or a crossover or wherever I can't help but smile. He's easily one of the most likable and fun riders out there.

Finished Ryuki the other week but only just got round to watching the movie last week and the tv special today.

So here's my list so far:
W
Kiva
Den-O
OOO
Kabuto
Decade

And now having watched Ryuki?
Ryuki
W
Kiva
Den-O
OOO
Kabuto
Decade

Yep, what an awesome series. The ending is a bit of a cop out but I guess it was the best possible way without ruining any characters. Everyone in a way gets what they wanted, it's beautifully executed and is emotional. I like how dark the show is and despite most of them being jerks you really get to like them and feel quite empathetic for them. I hated Gai though, what a douche. I also dig how it's pretty much Ren's story, first rider we see (blank form hardly counts =p) he gets his power up first and he wins... Sort of if Shiro hadn't erased the timeline...

I think if you can get past the first 5/6 episodes, the SFX/CGI/eclectic film style smooths out and it becomes a really good ride with some amazing suits and action.

Also, Kitaoka is the greatest character/rider ever =]

Yeah, Gai was a douche, but one of the best suit designs, imo. I watched episodes 20/21 last night, and they were really good.

I'm surprised by your ranking, but so far I'm enjoying Ryuki a lot, and though I'm only 4 episodes into Kabuto, I'm also quite enjoying that one. I think I'm not really going to be able to rank the series anymore, unless others are real stinkers, the ones I've seen are just all around great.