90% of the time you make more money individually.
10% of the time you make more money selling as a pair.
Here's the rationale:
Out of 100 people in the market for Tales of Destiny 1 AND/OR 2, 35 of them are probably looking for ONLY part 1, 45 of them are probably looking for ONLY part 2, and ONLY 10 of them are likely looking for both.
NONE of the people who are looking for just part 1 will likely be interested in paying extra to get part 2 as well
NONE of the people who are looking for just part 2 will likely be interested in paying extra to get part 1 as well
ALL of the people looking for both parts 1 and 2 might be willing to buy them separately as well (unless they can get a "deal" by buying both, in which case, you are back to making less money)
So, you can sell together and be marketing to only 10% of potential buyers - who are expecting to get a better deal by buying both together
Or, you can sell separately and market to that same 10%, plus an additional 35-45% of people who are only looking for one of the games.
My opinion...