Idk about you but the lego star wars games were pretty stuffty in hindsight.
Totally right. I remember having fond memories as a kid of the original two and being so hyped for Complete Saga, but playing it now, it's absolutely painful. The newer ones have the benefit of refinement and polish, but they still have a lot of problems (for example, LotR is fairly buggy, and Marvel Super Heroes made me physically ill which I've never been when playing video games).
That said, co-op improves any game since you're focusing on having fun together rather than the game itself. It actually works well, so long as you really are cooperating and not fighting over which character you have to play as.