As your points make clear, there are a lot of RPG-like elements in a lot of different games and game types, but that doesn't make them RPG's. I played a ton of Mail Order Monsters, maximizing my trainer (over 100 wins, etc.), though mostly using an exploit (you could use the robot drones to defeat the arena opponent rather than subjecting your beast to any combat). In any case, it was definitely one of the first monster raising/management and arena combat sims, but most certainly not an RPG. I always thought of Racing Destruction Set and Mail Order Monsters as inseparable, and, to a lesser degree, Adventure Construction Set (ACS). I still have my original boxed copies of all three for the C-64 from when I little. I never did finish my Doctor Who RPG in ACS...

By the way, speaking of ACS, would you consider those games RPG's? Technically, the games it came with and the games you could make qualified as RPG's, albeit with some limits, though certainly comparable to many of the earliest graphical RPG games.

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Bill Loguidice, Managing Director
Armchair Arcade, Inc.
(A PC Magazine Top 100 Website)
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