Which era has the most skilled players and the greatest competition overall?
Without question its the current era of Federer/Nadal/Djokovic. Fed and Nadal are 2 of the top 3 players of all time (if not top 2) and Djokovic is currently dominating them. Fed could easily win 2 more slams to put him at 18, 4 ahead of Sampras. Nadal will likely wear down in a few yrs so I'd expect him to top off at 12-13 titles. Djokovic has 2 and looks poised to grab everything in his path...
As for the field, the current field has to be deepest, most talented one to ever exist. Players train longer, harder, and more efficiently than ever, with more $$ invested in the gm than ever before.