Omega Ruby and Alpha Sapphire as a remake that adds new life to many concepts from the original Ruby, Sapphire and Emerald games. Several things are remodeled, as can be seen in the trailers.
Several Pokémon now have a Mega Evolved form. The most notable ones are the region's starters. Sceptile and Swampert will be capable of Mega Evolution, along with Blaziken (who got a Mega Evolution in X and Y). In addition to that, Sableye, Metagross,Salamence, Altaria, Lopunny, Slowbro, Audino, Camerupt, Sharpedo, and Gallade can also Mega Evolve (Diancie as well if you received the Pokémon X and Y event card from Gamestops, etc.). The item used to Mega Evolve Pokemon in these games is called the Mega Bracelet.
This is the new method opposite to evolution. Currently, only Groudon and Kyogre can devolve into their ancient forms.
Omega Ruby and Alpha Sapphire are the first remakes to feature 3D gameplay. The player can now move in all 8 directions. Some areas are also in 2D.
The starters are the same as they were in Pokémon Ruby and Sapphire. Grass-type Treecko, fire-type Torchic, and water-type Mudkip. The player has to choose one of them at the start of his or her journey.
Secret bases make a return in Omega Ruby and Alpha Sapphire as Super Secret Bases. Everything from the previous Pokémon game Secret Bases returns. The player is able to share secret bases using Street Pass or QR Codes. Player can also make people his or her, "Secret Pals" if he or she visits another person's base.
Sky Encounters are a new type of encounter introduced for the first time in Pokémon. This encounter can be achieved while riding MegaLatias or Mega Latios in Omega Ruby & Alpha Sapphire.