Depends upon your definition of "best." There are several that are quite good. The S&W M&P gets high marks for reliability and ergonomics.

The Glock 2x4, oops I mean Glock 21, has terrible ergonomics (too big, too fat, too squared off, not suitable for anything but open carry by someone with hands the size of a "Big Gorilla" (no offense to "our" Big Gorilla).

The SIG 220 is quite handy and the new 227 feels like a 226 in the hand, so it is not too bad.

HK makes the new HK45 and HK45 Compact, both of which are really nice.

Don't forget the Ruger SR45, which feels good.

Springfield's XDM is good, and has the advantage of using the same mags as the previous XD.

Springfield should make a single stack version of its new XDS in .45 ACP which mimics the size of the 1911 Government or Commander Model, holding 8 or 9 rounds in a single stack magazine. If they did, they would answer the call of literally thousands of shooters who have been begging Glock to do just that ever since 1990 when the G20 was introduced to much fanfare at the Las Vegas SHOT Show, where billboards on the highway from McCarran International announced the "Perfect 10" (the G20 in 10 mm). The G21 followed later that year in .45 ACP.

Unfortunately, the huge 2x4 feel of the supposed "Perfect 10" was eclipsed by S&W's announcement at that same SHOT Show of the FBI contract 1076 and the then-new S&W/Winchester creation, the .40 S&W cartridge and the then-new S&W 4006, and the California Highway Patrol contract. Glock just couldn't compete with that publicity that year.

So, which one is the best non-1911? I will have to go American and say S&W M&P, followed by Ruger's SR45. HK is quite nice, but magazines are quite high priced, hard to find, and HK is just not as friendly to deal with as S&W and Ruger, although admittedly better these days than years ago. SIG is last on my list. They are not consumer friendly, their guns are over-priced and not THAT MUCH better than the competitors. Remember when the SIG Classic pistols were first introduced? I do. The manufacturing methods were supposed to make them cheaper to produce, etc. Well, if it ever did, you cannot tell it by the high prices charged by SIG.