...IF it's appropriate to your environment. It's wholly INappropriate to mine.
Any non-NFA long gun is about as useless in my apartment as a bamboo cavalry lance. I couldn't even get it out of the bedroom door without hitting something with the stock or muzzle.
Where I live, I don't even waste time on a long gun. It's a handgun or nothing.
I think a shotgun is a fine choice for many people in many situations, but I agree. They aren't for everybody. For instance, I have far less experience with a shotgun than a handgun, and I don't have a range anywhere near me where I could practice with one. I have lots of experience with handguns, they fit in a drawer, so they are easily accessible, and 16 rounds of 9mm Ranger Ts or Gold Dots or a .45 in the hands of someone with training and tens of thousands of rounds downrange can be a pretty formidable home defense weapon. Also, if you happen to miss the all important first shot, a 9mm or .45 is going to be a lot faster to get back on target than a 12 gauge (or a .357 for that matter.) If I were going to choose a long gun for home defense, I would seriously consider a .223 carbine instead of a shotgun. I have no place to practice with one of those either, though. Again, I'm not saying that a shotgun isn't a great option. It is for many, just not me.
And since I mentioned .357, to me not only is it slower to get back on target, but the muzzle blast in a small room is deafening (potentially literally), and the flash has more potential to render you blind in the dark for follow up shots compared to a 9mm or .45. .357 is amazingly loud, even with ear protection at the range. Pretty much everyone in the adjacent lanes has looked around to see what I'm shooting. It is a pretty devastating round as handgun rounds go, though. If I were to use a .357 revolver for home defense, I'd most likely load it with good .38 hollowpoints, which would be quicker for follow up shots and lessen the blast and muzzle flash. Unfortunately, that would also lessen the destructive power, but there are some very good .38 self defense loads available, and they are much less likely to penetrate walls than a .357. There are always trade offs with these decisions.
Regarding revolver vs. semi-auto - a good auto is a very reliable gun. The two I have chosen for self defense, a 1911 and a HK P30, have both been 100% reliable with thousands of rounds. Semi-autos hold more rounds, and are, at least in my hands, quicker to reload. Many also have an integrated rail. I have a laser sight/flashlight combo on my P30, and it's a great tool to have for home defense. You can, of course, use a handheld light and laser grips with a revolver, but after six rounds, you have to reload, which involves two hands, so you have to put the flashlight down. Statistically, you probably won't have to reload a revolver in a home defense situation, but it is possible, so in my opinion, it should be taken into consideration.
But all that is just my opinion in my circumstances. A home defense weapon is an extremely personal choice, and there are lots of valid choices. I'm just pointing out that nothing is the "best" for everybody.
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