Bullet immunity, but no sword immunity?

Well...there's a lot of answers here...

So, in the real world, armour is rated differently. The same kevlar vest that will stop a bullet will be less effective or completely ineffective against knives. So, maybe conjuring energy barriers of different types is possible, but maybe it's harder to do for lightsabres than for blasters.

Or...it might not be the Force. It might be the armour (or a combination). Lightsabres are shown cutting through almost anything, but Luke scores a hit on Vader in his very movie, a hit which deflects off of his shoulder armour. Vader feels the hit, crying out in pain when it happens, but it doesn't cut right through. So, maybe his armour helps him. (I don't really like this explanation - it raises a tonne of questions and doesn't address Force masters' abilities).

Lightsabres are tremendously more powerful than blasters, though. Blast-doors are laser-bullet proof, but clearly not laser-sword proof, as demonstrated many times in the film. The quick damage of the blaster (a brief shot) doesn't compare to holding an energy blade (of considerably greater strength) against the Force master.

Different masters have different levels of power, too. Luke never displays the godlike abilities the Force can bestow while the original trilogy runs. He dimly glimpses the future, that's about it. He moves a few rocks. Vader is stronger, and maybe he can do it - that would explain the glancing blow. The only time Vader is sliced up by a lightsabre is his hand in Return of the Jedi, and he's already quite weak from a prolonged battle. Luke's also tapping into some serious Dark Side-y rage, so maybe he's willing the blade through Vader more than Vader can stop it. It might be harder to block than strike (as in real life - far easier to make a mammoth explosion than prevent that bomb/rocket from blowing a building apart).

Finally, though, the Force is just like a sonic screwdriver or R2-D2 or Gandalf's staff. Like any other sci-fi/fantasy techno-magic, it is a plot-driving stopgap that has whatever the writer needs. It's Q Branch from James Bond.

Now, I think this has become more and more obvious as the series goes on. In Star Wars, it was very mystic and ill-defined, but in a way that worked. Nobody really threw rocks with their minds or anything. It was Enlightenment. It was the ability to transcend death and be "bigger" than mortal universes or problems. By The Empire Strikes Back, it's also seeing the future and telekinesis - more magic powers type stuff.

And then each Episode seems to add new stuff and creates little plot-pockmarks (if not full plot holes) about "How come they don't just _______?"

I think, for the most part, they keep it just nebulous enough for me to buy it and just defined enough to be fun. The perfect balance was, for me, Gandalf. He always could help, but never cleansweep everybody, and it never seemed cheap when he did. Maybe because he came up against foes more powerful, we knew that he had limits. I feel the same way about certainly the original trilogy Force users. Luke can't capriciously pull objects around, they can stop blaster fire, but not sabres, and in general it makes them mighty, but not gods.

But, the short answer is: lightsabres are just a lot stronger than blasters.

Honestly with Star Wars and fantasy fiction in general there is a certain degree of obligatory suspension of disbelief that you have to enjoy it. Of course in more reason years under Di$ney Star Wars they've been pushing it to an obscene degree.

You're not calling it a universe?
Why do Marvel get a universe and Star wars dosent ? SW covers lots of planetes light years apart - its big.

I'm willing to assume that light sabers have Force-related properties of their own, and that Sith and Jedi cant affect another Force-user's light saber.

>If the ability to destroy a planet is an insignifigant power compared to what the force can do

Dont forget the other person with the lightsaber is also using the force to fight with and premeditate where the next light saber swing will come from

In the old EU comics, we did actually see Jedi masters able to deflect lightsaber blades without using a lightsaber themselves.