HenitoKisou: They are pills, not hearts, Doom2 has new kickass intermission screen, Map31 has these super-zombiemen. Also there's that Betray level. Many source ports including Doom Retro will detect and play BFG Edition wads just fine.
With Doom3 all these changes aren't forced but optional, you don't need use flashlight or ammo (not that I noticed, never found too much of it). I think there's more enemies in some levels, lighting feels more dynamic unlike original game. No hazmat or arcades is minor thing that didn't added a lot to gameplay. Performance is a lot better, I remember need to disable bump mapping and a lot of options down to just play retail without stuttering or lag, here it plays fine on shitty integrated graphics, except that porting to new engine raised RAM requirement to 3GB instead of 2GB because megatextures ragestyle, but it's still playable if you manually fiddle with settings and reduce that LOD.
-You are right about pills. Now it is going to drive me nuts about which censored id game had hearts on the health kits and what specific version as I'm 99% certain one of the classic id games had the crosses censored with a red heart.
-Intermission screen: Huh? Don't recall one. Can you be specific? Video on youtube you've seen with it? I checked a youtube playthrough but only checked the first intermission screen about Dead Simple and it had the usual brick background.
-Betray level: Its glitched. Using the exit reloads the level. Unless you use cheats. Having original XBOX version of Doom 3 and RoE that come with versions of Doom 1, 2 & Master Levels and having played PC ports of it Betray is NOTHING to be excited for anyway.
-Map 31:
https://www.youtube.com/watch?v=1snCRIl16ks Pretty sure they are standard zombiemen.
-Source Ports: Indeed. I have no reason to play the censored version of Doom 2 though. I only ever launch the nerve.wad with source ports and I've only played through BFG versions of Doom 1 & 2 for the achievements.
-Doom 3: Not forced. If you have to use the flashlight you use the suit flashlight... period. The gameplay mechanic of a carried weapon flashlight is removed. There is no 'optional' to that. Same with the ammo. Why would you NOT pick it up?
-Doom 3: More enemies: Almost certain you are wrong. Plan on replaying some classic id titles in the not to distant future and I'll double check then. If you're so certain of it perhaps you can produce a youtube video showing more enemies?
-Doom 3: Shadows: They're better in old Doom 3, unless they patched BFG edition.
https://www.youtube.com/watch?v=HPSVLI6lEoI ^ Seriously... the lighting and shadows are so much better in Doom 3 vanilla. It's oppressively dark.
Really, the only positive I can say for BFG Edition is that out of the box the textures look better and it supports modern operating systems, resolution and wide screen. Most of that can be achieved with tweaking or downloading mods though. BFG Edition is for console gamers or PC gamers who missed Doom 3 and want to see what the fuss was about... not for fans of Doom 3 has a horror shooter... with emphasis on horror.