Aeroplan is fine if you are able to get enough points to earn their "Distinction"status (not to be confused with Air Canada's Altitude status with Aeroplan). Once you earn distinction status, if you travel, you can get bonus points converting Marriott (you can set your hotel reward to autoconvert) and Starwood points to Aeroplan. With Aeroplan, the best way to earn points is by credit card. Charge everything you can to the card.
Aeroplan penetration to stores is not great (not surprising given target audience is different than airmiles). Before Sobey's switched to Air Miles, you used to be able to convert Sobey's points to Aeroplan points. If you knew what you were doing and followed the weekly bonus Sobey points offerings coupled with bonus aeroplan offers, you could game the system. People purchased hundreds of dollars of canned beans, tomato paste and KD at Sobey's over the years, coupled them with aeroplan multiplier offerings and got thousands of Aeroplan miles (averaging under a cent a mile). It was a sad day when Sobey's switched.