Success at being third? Was that even an improvement over Minolta, the company they bought?
Sony really couldn't compete in DSLRs. They made a bit of a splash with APS-C mirrorless. Their main accomplishment was offering the only FF mirrorless bodies for a few years. The A7's and A9 are what they are known for. You hear 'Sony, Sony, Sony!' so much from certain sites and 'influencers' that it's difficult to imagine the EOS M series out sells Sony in the only market where mirrorless out sells DSLRs, Japan. Yet it does. The mocked, derided, limited lens catalog, 'old Canon sensor' M series kick's Sony's butt in the most important MILC market in the world.
Neuro nails it every time he points out that the things we think about and debate on this forum are not the things that concern the average consumer or probably even the average professional. "DR, DR, DR!!!" yet what percentage of photographs are exposed ETTR RAW, processed for maximum DR, then printed to 16x20 or larger? 1%? 0.1%? 0.01%? I can count on one hand the times a freaking 11 stop 7D failed to capture what I wanted in a single frame, yet thanks to DxO and dpreview sensors are now judged ONLY by DR and Sony is 'so far ahead.' Give me a break. The R is sharper/more detailed than the A73 despite having an AA filter (something even Tony Northrup pointed out). This impacts every image taken. But 'Sony is ahead' because of a DR difference that would be nearly impossible to exploit. DxO biases their score to this tiny DR difference while
completely ignoring resolution and sharpness.
A number of Sony sensors, including the A9, have less DR than the 5D4/R but 'Sony is ahead.' The A72 had particularly poor high ISO for a FF sensor, well behind a 6D/6D2/RP, but 'Sony is ahead.' The first and second generation A7's suffered from off sensor flare, compressed RAW artifacts, and eating stars but 'Sony is ahead.' Both Canon and Fuji 4k footage grades far better than Sony's due to Sony's 100 Mbps limit but 'Sony is ahead.'
No, Sony is not ahead on every metric even when we look strictly at sensors.
It has a few very impressive specs but with Sony's typically poor ergonomics and poor weather sealing. It also has less DR than a 5D4 or 1DX II so clearly it's junk and Canon is ahead
Its competition is the A73. It has better stills IQ. It produces video that grades better but is worse at high ISO (due to the crop factor; stills high ISO is on par). Despite the fact that we Canon users complain a bit about the ergonomics, it has better ergonomics than the A73 (showing how spoiled Canon DSLR users really are by Canon ergonomics). It's better weather sealed. It has better/worse AF depending on the situation. It lacks some of the cool features of the A73 (like IBIS).
And at the end of the day, the differences are not going to matter in the hands of competent photographers / videographers. The guy who really wants IBIS for adapting old glass, or maybe high ISO 4k footage, is going to get the Sony. The guy who wants weather sealing and a touchscreen is going to get the R. Some other guy will decide based on what's on sale that week.
Small differences in select sensor metrics don't matter nearly as much as you imagine.