Since when?
Im thinking Chelsea Barca, ManU Madrid (iirc 0-0 first leg). Boring first legs, memorable second legs.
Just my opinion, but from what ive seen, the more technical Spanish sides tend not to go all out attack at home, they rely on breaking the opposition down slowly, whilst Premiership teams abroad tend to play defensively at this stage of the tournament, even the good footballing sides, hence why the away leg is normally slow and a bit boring - slow technical football vs defensive football.
The home leg is another story, as the English clubs tend to go on the offensive being egged on by the more vociferous home crowd whilst the foreign opposition quicken things up a bit, and thats when the game gets interesting, as you tend to have have attacking football vs technical football, more goals, etc.