I think that i should post my opinion too... I like Lucasarts games a bit more than Sierra's ones, thats true, but i like the adventures of Sierra very much also... In particular Space quest series of games, and Larry
From Lucasarts i really loved every game ( the only one i don't like is Monkey island 4 - The only game that should have never been 3D )... Simply because they are more funny than Sierra's ( and have better atmosphere too - Monkey island in particular ). Its the most important thing for a adventure game to be funny i believe... I play over over again, loading old saved games etc of Day of the Tentacle only to see its jokes again
I don't remember to have done this thing with any sierra game... Anyway... thats my opinion