Matlab-Simulink is still a good option for microgrid simulation as you have the possibility to use its own components (sources/renewables, ...) to construct you microgrid or designy ou own components if you are not satisfied or you are looking for better modeling accuracy/
With due respect to all those who have already answered, the best suitable software is the one in which you have best working experience. If you have expertise in matlab/simulink, you should proceed with that.
My feedback: Matlab/simulink is still the most popular choice among researchers. Others options being PSCAD, RSCAD (the one which comes with RTDS). There are many other simulation platforms. But ultimately it all comes down to a group of organizations trying to lure researchers with their lucrative toolboxes and promotions via institutional tie-ups.
Go ahead and use the one you like, may the force be with you!