that depends who u ask, but run a drag strip and 4cyls will own the twin almost always... however get to the track and thats arguable.. Ducati's racebike is 220HP and faster then hell. they do well in racing.
Better is a objective word.... Different is a factual statement.. a Twin is much different then a 4 cyl to ride.you have to ride both to know what its like to compare em. I have a 4 cyl 1000CC bike and my 500CC Twin is still a blast to get on, its really light and the feeling is refreshing once in a while, no 4 cyl will put power at the wheel right off the clutch like a twin... Even my 500 twin will launch harder then the 1000...mostly out of fear of goign to hard on my 4 and gettign on my @$$...but the initial power on the drop of the clutch is what makes me love a twin.. i'll always love em... someday ill own a bike like a Aprilia or a TL1000.