Comparably..
Comparably to Ruby and Sapphire, its the same, except for the story is better as you fight Magma AND Aqua, you can get both of the fossil pokemon, you can catch Kyogre AND Groudon, theres more end game stuff. Like Artisan cave, smeargles are awesome for breeding as they are in the ground egg group. Also you can catch Ditto where you get the second fossil.
Also there are some small tweeks, the pokeballs light up when you successfully catch, the text is smaller and less atrocious, more trainers to battle, and then upon completing HoennDex, you can pick from Totodile, Cyndaquil and Chikorita! The Johto starters w000t! The battle frontier is fun also.