I gotta be honest, the ECW title hasn't really had a truely great champion since it was brought back, it didn't really help anyone's career all that much, and each holder either got fired, or went straight back the mid-card after their reign. however I'll examine each champ a little bit.
Rob Van Dam
Well if you're gonna base it on name power, RVD was one of the top guys to hold title, and with this he became the only guy to hold the WWE and ECW title at the same time. However with that said, his reign was really anti-climatic, mostly due to the fact that he and Sabu were caught with drugs. I believe he only had one actual title defense before loosing it to Big Show less than a month later.
Big Show
Like him or not, I consider Big Show probably the best guy to hold the ECW title since it was brought back, it seemed to have meant something when he held it. he had a great feud with Sabu for it, then multiple wrestlers from other brands came to ECW to fight in Extreme Rules matches for the belt. When guys like Ric Flair, Kane (who later won it), Batista, and The Undertaker came to fight Big Show for it, it felt like it was an actual world title. Plus with Paul Heyman as his manager, Big Show's reign was probably the best.
Bobby Lashley
I'm still undecided with this one honestly, I mean Lashley held the title twice, the only guy to do so since the title was brought back, but his reigns lacked truly memorable moments. I guess you could say by this time ECW was become more WWE'ized so to speak, Heyman was leaving Big Show was gone, and the ECW originals were becoming less important. Anyway, so Lashley wins in the Elimination chamber match, defends it against Big Show, and then what? Feuds with Test for a little, then has a few good matches with Hardcore Holly, gets invovled in the Battle of the Billionaires, then looses it to Vince.
Vince McMahon
Not much to say here. I always took this as Vince's way of saying, 'yeah ECW is mine and I'll do what I want with it.' After a few Handicap matches with Lashley, and a face off or two with some ECW originals, Vince looses it back to Lashley at One Night Stand 07.
Bobby Lashley #2
Once again not much to say here because Lashley is drafted to RAW and the title is vacated a few weeks after he won it.
Johnny Nitro/John Morrison
This reign was never actually supposed to happen, but after the Benoit tragedy, Vince decided to put it on Nitro, afterward he became John Morrison and had a halfway decent run. I do consider this the reign though that began the transition from World title to Mid-card title for the ECW title. After a few run ins with Dreamer to push Morrison, and a run in or two with Boogeyman him and CM Punk had a great feud for the title with some great PPVs matches a the GAB and Summerslam, before loosing it to Punk on ECW.
CM Punk
To the best of my understanding CM Punk won the belt from Morrison because Morrison was suspended, but whether or not that is true, Punk was gonna win it eventually. i'd probably say the most memorable part of this reign was his feud with Elijah Burke, two young guys who (at the time) had bright futures ahead of them, fighting for their spot, it was probably Punk's best feud up to this day IMO. Anyway, once that was done, he feuded with Big Daddy V, Mark Henry, The Miz, John Morrison, and finally Chavo, before loosing to Chavo. His reign over all was good, he had some good matches both for the title and non-title against the likes of MVP, kenny Dykstra, and Jamie Noble. But it ended in a very bad way, and that kinda overshadowed his whole reign.
Chavo Guerrero
This was a really, really, bad move. Chavo comes back from a suspension/hiatus, has three matches with Punk that end in a no-contest, and then beats Punk for the title when Edge interferes. I guess Chavo became champ to strictly further the LA Familia storyline that was going on. OVerall a short reign that saw only one memorable moment, when he lost it to Kane in an 8 second match.
Kane
I'm a Kane fan so I was happy to see him win the title, but I still don't see why he actually did win the title. He was involved some feuds with Henry, Big Daddy V, and Shelton Benjamin on ECW, but was never actually an ECW wrestler when he won the title, all in all it seemed rather random to me. But anyway, his title reign to saw few memorable moments, I mean he wasn't even apart of One Night Stand when he was ECW champ. After a title defense or two against Chavo, and teaming up with Punk in a failed attempt to win the WWE tag team titles from The Miz and Morrison he lost it to Mark Henry at Night of Champions.
Mark Henry
This reign really helped bring back Mark Henry's career. He went from a jobber to the stars to an actual threatening member of the roster. Henry is a good monster heel, although a lot of people don't like him, his reign was great, although to short. After feuding with Dreamer, and then defended it against Matt Hardy at Summerslam, he lost it to Hardy in a championship scramble at Unforgiven.
Matt Hardy
Once again not much to say. I don't think anyone was actually surprised by Matt Hardy winning the ECW title. He was drafted to ECW for he sole purpose of winning the title IMO, to continue the momentum of his singles push after he won the United States title. Not much to say about this reign though. After he defended it against Henry a hundred times, Finlay a few times, and had a really brief feud with Koslov he lost the title to Jack Swagger.
I'm not gonna talk about Swagger's reign yet as he still is a new champ.
But yeah, those are my opinions.