When Fidelity's Amex had the Worldpoints to Aeroplan conversion, I felt that card was the best card for uncategorized spend. 2 Aeroplan miles/$. Now, that conversion is gone, so the redemption only earns you a straight 2 cents/$. That card is trumped by Barclaycard Arrival, which equates to earning 2.22 cents/$.
I personally happen to think that the best card for uncategorized spend now is the Club Carlson Premier or Rewards visa. I feel that for me, 5 Carlson points is worth more than 1.5 United miles, 2.22 cents, 1 starpoint, etc.