The battery life is going to be 2.5 hours for movies, and those are reading the disc the entire time, so naturally the lowest battery life for games would be 3 hours. Games that don't read the disc continuously can have the battery life last upto 8 hours. (this is direct from Sony)
System launches rely heavily on sequels, so it's not surprising that many of the games aren't original yet. It's safe business practice to release sequels on a brand new platform anyways, that way you aren't risking putting all that new development and ending up in the red. Another thing is, all consoles have seen sequel after sequel in the last few years, it's the current trend in the industry.