Here's a tip: There's more to Smash Bros. than just people with swords. Sure, they have long reach, but if you learn to dodge properly (dodge rolling, side-step dodge, know what you can shield against and what not), you can oust any foe.
Another tip to help you get good: Dodge-roll, dodge-roll, dodg-roll. It's your best friend. What I try to do is dodge-roll behind and use grabs and throws. Try to give as much damage (without taking more than what you give) as much as possible. Learn to dodge well. Timing's good, too. That's really all I can say.
And Luigi IS the man. He's an awesome aerial fighter. His jumps get lots of hang-time, but when you're trying to get an item that's a level aboe you it can be a pain. His fireballs aren't affected by gravity, his Green Missile can throw people off from guarding it if you get a misfire, but it can also be your worst enemy. So it's a good idea to use it sparingly. It's an awesome recovery move as well. His up+B can only do 1 damage, but if you're "inside" the enemy, it turns into a fire punch (and makes a pleasing 'clang!' sound as well) for very decent damage. His down+B can move a vast distance, so it makes a good "dash" attack.
I'm telling you, this guy rocks.
