How many model parameters did Microsoft's 2015 ImageNet-winner network have?
The number of parameters is 60,344,232, according to:

https://resources.wolframcloud.com/NeuralNetRepository/resources/ResNet-152-Trained-on-ImageNet-Competition-Data

Although, from https://arxiv.org/pdf/1512.03385.pdf (page 6), it looks like an ensemble was used for ILSVRC 2015:

"We combine six models of different depth to form an ensemble (only with two 152-layer ones at the time of submitting). This leads to 3.57%
top-5 error on the test set (Table 5). This entry won the 1st place in ILSVRC 2015."