Both games now offer an increase in framerate from the original 35fps to 60fps for smoother gameplay, and a new aspect ratio has been added that stretches the display vertically to match the original 4:3 aspect ratio that the game was intended to be played in.
There's also added support for quick saves and a new option to select any episode, map, and difficulty setting for immediate play, without having to clear the previous levels first.
Perhaps the biggest addition though is support for DOOM and DOOM II community add-ons. These will be curated and offered as free downloads from the main menu, and Bethesda says that it is open to suggestions as to which community-made episodes it should include in the future.
As it stands, players can load up John Romero's SIGIL, as well as TNT Evilution and The Plutonia Experiment, the latter two forming 1996's Final DOOM release. As noted by our sister site TouchArcade, DOOM II also gets No Rest for the Living, which is a map pack originally available on Xbox Live.
Gamers will need a Bethesda.net account to access the add-ons, but the good news is that Bethesda has removed the online log-in requirement that caused so much frustration when the games were released last year.
A full rundown of all the updates and improvements can be found here. DOOM and DOOM II are available to download for iPhone and iPad from the App Store and both games are priced at $4.99 each.