That doesn't make a better game. Just means more variety. I didn't enjoy many of the Reach gametypes. Invasion was only mildly amusing.

: - More Custom options

Fair enough.

: - Campaign scoring

Fair enough. Not a huge deal to me, but I do miss it.

: - No perks

That doesn't make a better game. Though I enjoy an equal playing field, the perks are relatively balanced without one dominating other players.
You can always play a playlist without them if you want.

: - No random-ass ordnance system

Rewards for good play aren't a bad thing. And as everyone gets them equally (albeit random choices) it balances out. Don't squander your ordinance, basically.
You can always play a playlist without them if you want.

: - No rank-based weapon/ability unlocks

The real thing to blame here is Reach's introduction of Loadouts.
Rank-based unlocks is a little bad, but again, it isn't going to sway the tide of battle after you have played a handful of games. YES, it is bad before you unlock the DMR/BR/Boltshot but if you are making your judgement call before you have played enough to unlock them, then you have not played long enough to make a judgement call.

: - Better HUD (it had a health bar, red X's, a compass, etc.)

Red X's are the only legitimate thing here. Health bar is useful but it isn't hard to tell how many times you have been hit.

: - Better AI

Do you not remember Kat? I vehemently believe that the AI in Reach was broken. Halo 4 marines drove me around quite skillfully in vehicles.

: - Various useful Forge tools (e.g. fine-tuned movement by clicking LS,
: zooming in while in Monitor mode)

Fair enough

: - Better camera in Forge

I guess a little.

: - Forge World

What about it? The size? You now have multiple maps with varied environments to do your forging in.

: - Theater for Campaign

Fair enough.

: - Less weapon redundancy

And consequently less entertaining weapons.
Much like you say that Reach has more gametypes I could say that 4 has more guns. Neither are an absolutle positive or negative, what we should look at are which guns make the game more fun. And to me, the variety of 4 does this. I barely even see weapon redundancy in Halo 4.
Snipers: Human better for long range, Covie MUCH better for Snapshots, Binary clearly different.
Mid/long range: DMR and BR are similar but notice that almost all pro players use the BR. There is a clear difference in their effectiveness.
ARs: I don't know many people that care about these guns, but why bemoan having extra visual options?
Pistols: All VERY different functions
Flagnum: Weird but it has added a brand new and fun dynamic to flag carrying
Shotguns: Rapid fire shortrange VS slow fire long range. Scattershot is going to be more useful in open environments. Generally the Scattershot is not as much of a power weapon. This is a good difference.
Rockets: All ENTIRELY different behavior. (Fuel Rod usually sucks ) Incineration is even far more dangerous to the user.

: - Fewer visual retcons

That doesn't make a better game. Story retcons are far more heinous than visual ones.

: - Mjolnir that looked like Mjolnir

Mjolnir has been changing since Halo 2. You have to expect things like that to change for every game.

: - No QTEs

Fair enough. The only heinous one was really at the end of the game though. I really don't understand that decision.

: - Playable Elites in MP
This was a novelty at best. Aside from Invasion I hardly ever played as Elites and it only felt like a novelty anyway.

: Meanwhile, Halo 4 has the following improvements over Reach:
: - Better weapon balance overall. It's still got its flaws...

You play this down too much. Weapon balance is a HUGE part of what makes a game fun. It is the thing that gets complained about most as to why successive Halos are not as fun as teh previous. Good weapon play is what makes multiplayer enjoyable, coupled with good map design.

And to me Halo 4 has much better map design. Haven, Exile, Monolith, Skyline, Adrift, Abandon, and even Complex for certain game types are fantastic. Again, see MLG/AGL for confirmation.

More than this movement (again a big fun factor) is much better and entertaining than in Reach. Sprint was long overdue and the jump height an movement speed makes for great gameplay and great competitive shootouts.

Perosnally I also thought that the campaign missions in Reach were far too boring, flying around New Alexandria with no overarching goal is still a chore. That's teh problem with Reach, it had nothing for you to strive for in the campaign. They were almost all short term goals. Nothing kept me wanting to play. More vibrant settings (like in Requiem) might have helped. The characters in Reach had me squirming at cliche's the whole time, while 4 was generally much better about proper development.