I have been reloading since around 1970 or 71, and have seen many new cartridges come and sometimes go over the years. Although there ARE exceptions and I am speaking MY OWN opinion, I have seen "one" MAGNUM that I believe fills a niche that was void, and as I said this is MY opinion and no one has to agree.
The 357 magnum FAR IMPROVED the 38 round, "in a medium framed pistol", and statistics have continued to prove this out, mostly in the Law Enforcement arena.
The 44 magnum cannot do ANYTHING any better that a loaded up 45 Long Colt, and a loaded up 4570 will do anything the 458win mag will do in reasonable ranges for both.
The magnum craz over the last 30 years or so has come up with NUMEROUS cartridges that fill the testosterone needs of the younger crowd, but the old reliable calibers used by myself and my grandfather continue to prove that less is not only cheaper, but sometimes better, and most of all, ADAQUATE. In the thread on good moose gun calibers, it is entertaining to read the reasons for this or that, and to know that in reality, in Canada, and Alaska, many of the old guides, and locals are still taking moose with the 3030.
If magnum melts your butter, then so be it as I view it as a preference, not a necessity. SHOT PLACEMENT is the crux to clean kills, and many a "magnumite" has believed that his magnum will MAKE UP FOR, a poor shot, and 99% of the time, it will not! JMHO