Okay here we go.
Having decided to purchase a rifle, we must decide whether it will be used primarily at close to mid-ranges, or mid-to-long ranges. For the sake of argument, let us call "close" fifty meters and under, "mid" fifty to 300 meters, and "long" everything beyond that.
Any serious shooting out beyond 500 meters puts the 5.56 cartridge out of the game, as well as the 7.62x39. The Russian cartridge because the trajectory is such that you have to aim the damn thing ten feet above the target's head in order to have a prayer of hitting anything, and the 5.56 because you might hit something out beyond 500 meters, but that little .22 caliber bullet will have expended so much of its energy that you won't do your target much damage.
Do you want to hunt big game with this rifle? Then definitely forget about the two assault rifle calibers. They might be fine for coyotes or prairie dogs or feral hogs at close range, but not for mule deer or black bear or elk.
So. A serious rifle, in a serious, that is to say, a full-sized caliber. This means 7.62x51, .303 British, 7.92 Mauser, 7.5 Swiss, 7.62x54 Russian, or good old .30-06.
You will instantly notice (or at least you should) that these are all military calibers. The reason being that sporting rifles simply are not rugged enough for what you probably want to use them for. Plus ammunition for military rifles, while it has been getting more expensive, is still more easily purchased in bulk at a discount. Which is good because you will be practicing a LOT.
Now, your choices at this point are between bolt-action rifles (Springfield, Enfield, Mauser, Mannlicher) and semi-automatic rifles, either clip-fed (M1 Garand) or magazine-fed (lots of choices).
First, let me say that the advantage of the high-capacity semi-automatic rifle diminishes as the target gets farther away. If you are regularly engaging targets at 1000 meters, then you would forget about automatic rifles altogether. But you want this to be a general-purpose weapon, so we have to take multiple targets at close range into account.
A good man with a bolt action can be as deadly at mid-range as a good man with an automatic. Better, even, if ammunition is low, because with a bolt action it isn't as quick and easy to waste ammunition. But if you anticipate close-range action, a box-magazine semi-automatic rifle is probably what you want.
So let me go down the list of the most popular choices.
Fabrique Nationale FAL
Heckler & Koch HK91
Springfield Armory M1A
Let's first talk about the ones that didn't make the list:
The Kalashnikov is a good rifle for its role, that is a cheaply built, easily maintained hunk of iron that will keep shooting until Doomsday as long as you keep feeding it ammunition and give it an occasional squirt of grease and shake out the mud. However, it is of questionable utility at long ranges, and ergonomically it is a nightmare.
The AR-15/M16/M4 platform is not a bad design, and it has a long (if not entirely spotless) military record. It's not as rugged as the Kalashnikov, nor will it shoot for as long a time under adverse conditions without catastrophic malfunction as the AK. Its biggest drawback is the inadequate caliber.
The M1 Garand is the rifle that won the Second World War (not really. Springfields, Enfields and Mosin-Nagants played a much bigger role), and the big, robust 30-06 is a very serious cartridge. But it's a long, heavy, ungainly rifle, and you can only carry eight rounds before you have to reload. Plenty of Japanese, German, Korean and Chinese soldiers were killed at short range by it, but this does not mean it is a good short-range weapon.
I am going to eat, then post what I like and dislike about the "big four" and their clones and cousins.