I've played through it about three whole times now. I played the Rare Replay version all the way through twice (don't ask) and I've finished Live and Reloaded one time. I think I've probably sank in 30 or 40 hours into the campaign.
I will agree though that the OG's multiplayer modes are superior to LaR. I don't understand why Rare scrapped it, but my guess is that maybe they felt that the original's formula was good and wanted to rework it so it was better for Xbox Live. I think that was the main selling point for the game, as in its promo material almost always brings up the Xbox Live aspect and glosses over the remake of the story mode.
Though, I admit I never thought of Conker's Bad Fur Day as a multiplayer game, especially not LaR, ironically. At least the OG's multiplayer is straight forward, but in LaR I played with my brother and a couple of friends and we just couldn't figure out what the hell we were supposed to do