Let me see, as far as new mechas are considered...
Argevollen was pretty bad, Aldnoah.Zero was kind of bad, M3 was probably bad, Captain Earth was certainly bad.
Knight of Sidonia was maybe good? I didn't really watch it.
I don't really watch much mecha at all to be honest, so I can only somewhat represent the taste of my surroundings, and I haven't heard of anything all that great as of late. I think I heard some people be excited over Soukyuu no Fafner, although that seemed to be a sequel.
There's always Cross Ange, I suppose, if you're into that. It has an admirable trainwreck quality to it that keeps me watching.

I thoroughly enjoyed Argevollen, personally, though I can certainly understand it wasn't as good as it could be. I'd definitely still recommend giving it a go.

Captain Earth was adorable. And there were mecha sometimes.

I really should finish M3 at some point, but that just was terrible. Still, want to see a bunch of mentally scarred kids try to pilot mechs? Might be for you.

I suppose Cross Ange is a mecha, but I really can't get past how dull our main heroine is.

As for Aldnoah.Zero...I'm enjoying it. I can see many flaws, but it's still fun to watch.

There was also Nobunaga the Fool. That show was silly ahistorical fantasy, but it was different.

Oh, I'm enjoying Aldnoah.Zero as well, but I wouldn't call it good. Inaho is so grating, but I really want to like him for various dubius and strange reasons.

It appears Unlimited Fafnir is the latest incarnation of "Guy with Special Powers otherwise only found in Girls attends previously All Girls School." The only question is whether I should risk it despite knowing how these shows tend to play out or just abandon it now before I get bored with it midseason.

Well, if you don't like it, you could always watch Absolute Duo, Sekai Tsukai no World Break, Maou no Testament or ISUCA if you want another flavor of generic supernatural harem pandering.

The first episode of ISUCA was some of the worst anime I've ever seen. And Absolute Due would require me to pay Funimation, use Hulu, or pirate it, none of which thrill me. As for World Break and Testament, I will probably be getting around to watching them soon.

Felt like doing another one of these:

What is your least favorite arc of all time in an anime you have liked?

It's hard to think of anything to top Endless Eight from Haruhi.

Hey Mr. They worked very hard on all those costume changes.

Endless Eight is indeed one of the main contenders for being 'that arc'.

On the rest I mostly watch 1-cour anime so there's not as big a chance of an anime having multiple arcs.
Stuff that I remember and did not like so much:
Yumekui Merry: The last arc was anime original and horrible compared to the source material that could've been used.
Azumanga Daioh: I felt like the later vacation sessions were just reruns of their first year vacations.
Minami-ke: Anything involving the anime-original character in season 2.
Toaru Majutsu no Index: The arc in Italy on the boat.

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In other news: Dog Days '' does exactly what I expected.
The demon war lasted one episode. Still action-packed though. Demon was a plant-like monster so the sort of fanservice was also expected.
Last hero got a Crystal that transformed her into adult form and was by far the best transformation sequence. Not boring like Shinku, and not overly lewd like Rebecca.
And the war ended, heroes reunited with their rulers. The new character stays behind in her forest to make sure everything is ok (hope we see more of her later).
Most likely back to normal stuff next episode.

Let's not get the impression that I consider any of them anything more than trash.
Although I did love one of the expressions in ISUCA.

Not sure if I can contribute much in the arc discussion. I don't really watch things that last that long. I suppose it would have to be from Kuroko no Basuke, Monogatari or HxH, but nothing comes to mind.

Hands down, by a margin wider than the Grand Canyon, is the Alfheim arc from Sword Art Online. The amount of compost in that arc could fuel a third-world country (hyperbole, of course).

But maybe that's not the correct response. You did say "least favorite" after all, not "most hated".

I think the only one I have that qualifies as something I liked but wasn't as strong as anything else would have been the first two episodes of Blue Exorcist, possibly followed by the second season of Durarara!!. The former made me want to not watch it (though I'm glad I stuck through the first two episodes), while the latter simply didn't feel as strong.

Even if you think they are all trash, surely you can agree even garbage can be have better or worse than other garbage. ISUCA was terrible for a number of reasons. The characters were very bland. I saw almost no effort made to show any aspect of the characters' personality aside from the brief discussion the MC and his buddy had. They had your typical ecchi moments, but a combination of severe censorship, rushed timing, and, personally, the artstyle ruined any potential benefit from the fanservice. The monsters were only interesting for the brief moment they were introduced, then became just fodder for the lead heroine. And, sadly, due to all the wasted effort on ecchi barely anything in the nature of a plot appeared. And at the end of it all, I felt that nothing had been worth my time. The most interesting part of the episode was the opening scene when I thought this might be an intense horror anime.

Now, the first episode could misrepresent the series as a whole. It has been known to happen. At the same time, that was some of the worst anime I've sat through in that first episode.

Haven't yet checked out the others I mentioned, though I plan to get around to one of them today, but I expect they will be better by miles than what ISUCA was even if they are all cliche ecchi harem shows with little to no plot or character development.

That is right. ISUCA is the worst episode I've experienced in a long time, without any resemblance of competition.

I dropped ISUCA manga halfway through vol 2, which is pretty rare for manga I pick up.
Granted, I was expecting something a little more kyudou related.
I mean, when the symbol is of a girl holding a bow, what else were my supposed to expect?

I am amazed someone thought it was a good idea to animate that thing.
Then again, there's been worse stuff animated before...

I got the impression that people on /a/ that had read the manga were pretty excited for ISUCA, up until the episode started airing.

In an expression of boredom, I watched some more Absolute Duo, and I suppose it's not offensively bad. I manage to enjoy myself every now and then.

So my friend says I'm not allowed to say an anime is bad unless I've read the manga and/or played the video game. Like..... all anime.

My opinion is that if it can't stand on its own then it's not a good anime, with a few very rare exceptions.

Thoughts?

Your friend is either dumb or you're misinterpreting him.

This but with every form of adaptation. Anime, TV shows, movies, video games. Doesn't matter what it's derived from if it can't stand alone it is bad at it's singular purpose.

Not misquoting him. Apparently I am a "filthy secondary" who doesn't know the beauty of certain series because I haven't read the manga and thus am not able to follow it properly.