Something should be viewed as a success if it advances storylines, adds a new dimension to the show, or improves the overall product within the ring. The guest host concept did not of these, and often times detracted from the aforementioned criteria. If there was a choice for "epic fail", I would have picked it.
The guest host concept started off fairly well with Batista and Ted Dibiase Sr., as both were active/former wrestlers, and contributed to the product. Batista used his power as a means of helping to settle his grudge with Randy Orton, as well as set up the NOC tournament to see who would face Randy Orton for the title there. DiBiase's week saw him set-up the triple threat match between Orton, HHH and Cena at Night of Champions, which really jump started the huge feud between Cena and Orton last year. It also created a nice backstory that allowed DiBiase Sr. attempting to do what he felt was best for his son, but DiBiase Jr. just didn't get it, which came off as an emotional, heartfelt moment that reminded viewers how good DiBiase Sr. was on the mic, and served as a catalyst for him being the "feature presentation" of the Hall of Fame class this year.
It was all downhill from there however. Instead of furthering storylines, we got campy comedy scenes including a litany of gimmick matches between Chavo Guerrero and Hornswoggle. It also put non-wrestlers in the ring in high profile matches time and time again. Guys like Seth Green, Cedric the Entertainer, Jeremy Piven, and John Heder had no business stepping foot inside the ring, and not only did they do that, but they wound up pinning established superstars. However you spin it, that's detrimental to the careers of the superstars who are pinned by these Hollywood actors wh've never taken a bump in their lives.
It also created alot of contradictory booking. Instead of having a heel GM who ruled in favor of the heels and had personal agendas with the faces, or face GM's who were unbiased unless crossed, we got Guest Stars doing one-off's and getting unlimited power for the week! Beyond that, we would see one Guest Host in heel mode one week, and another Guest Star in face mode the next. It made for awful booking and poor storyline advancement as they became the center of the show rather then the Superstars, which is an insult to the wrestlers.
This could have worked if they would have used ex-wrestlers on a weekly basis who furthered storylines, much like the earlier ones did. But once they set foot in the ring, or turned it into their own variety hour, it was all downhill from there. I tune in to Raw to see John Cena, Randy Orton, Sheamus, and The Miz, among others, not Jerry Springer, John Lovitz, Jewel, and the Osbournes. It was a waste of time and counterproductive to the overall product, and I for one am glad the concept is over.