Annex was a spin-off of the Marvel vs DC series. I thought it was going to be a dude who sorta went between universes without control, but he was supposed to protect the boundaries between the universes and enlisted guest stars every issue to help. I don't care how neat it was the first time, how cool both characters are, or whether the Annex comic was considered canon in both universes, you can seriously only have so much sexual tension between Jubilation and lil' Timmy Drake, especially when it's pretty much a no-no to have it permanently affect them in their own titles.
Or am I thinking of Access? Ah well. Either way it sucks.
Marvel vs DC could've been great, but it ended up sucking. The match-ups were silly. I think I said in the "Comic Character Showdown" thread how incredibly ludicrous it is that Wolverine could ever beat Lobo. Wolvie's tough, but he never killed off entire worlds because he felt like it or gained immortality by scaring the occupants of both Heaven and Hell.
The Amalgam books were hit and miss. Some were fun, like "Dark Claw" (I think that was the name). Given that James and Bruce wear similar costumes, have goofy kid sidekicks who wear similar costumes, and have the same attitude, they were born to cross over in such a method.