I have two suggestions for the end of ROTJ if they aren't mentioned yet:

1. Make the scenes longer! Put together scenes from the same place (choose between Endor,space battle or Luke/vader fight). For example the scene when Luke is winning over Vader and the emperor says "so be it, jedi" the scene should continuee with a short scene of Luke, then back to the emperor saying "If you don't want to be turned you should be destroyed!", make this a single sequence. When ultimately Vader (hurt) lays in Lukes arms, not until then they should cut to Han Solo running from the soon exploding base, and also put togehter the scenes when the rebel ships is attacking the death star in a long roller couster sequence. Today the scene doesn't work because they first show the emperor, then the rebels, then BACK to the emperor like no time at all have occured (see the soap opera "the bold and the beautiful" for the art of stopping time!).

2. Put something in the reactor room! When the rebels fly in the reactor room it is very empty, no defence what so ever. I think it should be more difficult to get through, maybe some AT-ATs on the floor (!), flying tie fighters and some sort of inner shield protecting the reactor (maybe something similiar to the shield that surrounds MCP (the bad guy) in "TRON". Think videogame here, this should be the hardest room, not the easiest (just to fire in the middle is too easy and no tension, I think). This is the final episode of Star Wars and this should be the climax of the roller couster rebel attack, it should be breath taking (look for Simpsons ride-roller coaster at Universal studios for inspiration), see youtube http://www.youtube.com/watch?v=jJGHCQXFlnM) also maybe the reactor room should be upside down or turned 90 degrees to the left or something.