The answer is no.
The top 3 is probably the strongest ever, but Murray isn't a strong enough #4 to make it the best top 4 ever. McEnroe, Connors, Lendl and Wilander probably take that title.
What? By the time Lendl and Wilander showed up with their best years, McEnroe and Connors were done winning slams... I mean at least right now, Djokovic/Federer/Nadal are grabbing titles and Murray is certainly just one step behind them. If anything when it was Borg, Connors, McEnroe and perhaps an early Lendl which could be a similar comparison to now would be a more relevant quad.