Starting First Baseman:
The last couple years, he has absolutely CRUSHED pitching and has two consecutive seasons of 35+ Home Runs even when 35+ Home Run Seasons are becoming less common. Even before the last couple seasons he had some pop in his bat but it took him awhile to be the veritable force that he has been the last couple of seasons. He's even thrown in a little bit of speed, stealing 20 bases over the last couple of seasons.
The seven years before 2011, he was a decent hitter capable of hitting about 20 out but wasn't a highly valuable fantasy baseball asset during those years. When he get traded to the Blue Jays, I was relieved that he was out of the NL Central because he always seemed to crush Brewers pitching. Defensively, he has been sub-replacement level for a long time which could eventually force him into being a DH. Also, he's on the wrong side of 30 (31).
His most similar hitter through age 30 is Torii Hunter. During his age 31 season (2007), Hunter busted out a .839 OPS and threw in 28 Home Runs and is still an above average performer several years later (even if his power numbers are slowly declining.
This one is pretty obvious, Encarnacion is a keeper. It may have taking awhile for his bat to become a force but he has proven that his strong performance hasn't been a fluke. While he may not be a household name such as Fielder or Goldschmidt Since I have four other players with first base eligibility, adding anyone at first base on to my watch list would be counter-productive.