I need help again .i know you this

The storyline is far from over.

Other legendaries you can catch:

Regigigas- migrate the three Regi's from Ruby/Sapphire/Emerald, and go to the bottom of Snowpoint Temple in Snowpoint City. The "statue" you see will come to life, and battle you as a level 70 Regigigas.

Giratina- found in a cave along the east of Route 214. The area before it appears once you obtain the National Dex, which you have. My point is, is that you might not have noticed it, yet. Anyways, go in there and in the cave. The cave, whose name I forgot was called, is totally random. There is no specific way to go through, each room you'll enter is random. What is guaranteed, however, is that entering the room you just came from will bring you back to the beginning. Anyways, once you manuever through the cave and pass through three rooms with a pillar in the middle, the next room will be a room in which Giratina resides. He's level 70, and is known to be the third of the "trio" of Dialga and Palkia.

Cresselia- go to Canalave City and talk to Sailor Eldrich. He'll take you to Fullmoond Island, where you'll find Cresselia fly off. Pick up the item, go back to Canalave, give the item to the Sailor's son, and track down Cresselia like you did with Mesprit; with the Marking Map. It's a female and level 50.

This is just legendary pokemon. There are other things you can do, such as beating 100 battles in a row in the Battle Tower, catching other Pokemon in the PokeDex, doing some Pokemon Contests back in Hearthome City, etc.
You can also make a team consisting of your favorite Pokemon and favorite moves. Leveling them up to level 100 is challenge, but it's worth your time.