Ok, instead of saying Dragon's Lair, lets say Heavy Rain gameplay is like the dialogues in Mass Effect then?
Essentially that's an improvement over Dragon's Lair, by branching the story line to multiple choices and outcomes, but in it's core it's the same - an interactive movie.
Like the dialgoues in Dragon Age (I suppose they are very similar in their structure to Mass Effect's) - I didn't feel like I was playing a game when I did the dialogues in Dragin Age: I felt like I was watching, or rather "directing", an interactive movie.