Thoul wrote:For the
Phantasy Star Gaiden logo in the
Phantasy Star Complete Collection image galleries, the typical "Phantasy Star" text was omitted. It is part of the logo on the box and in the game, but is identical to the same text used in the
Phantasy Star II logo. So instead we have just the "Gaiden" text. And although this is in Japanese, that is what it says: Gaiden. You can't get a more clear indication that this game was a side story to the main saga than to have it in the name.
I believe it's not that linear. "Gaiden" is not always that literal and could mean some other things. For instance, Gaiden may also mean "Anecdotes" (short and amusing/interesting stories about an incident or person).
Just to give a concrete example, "Tears to Tiara Gaiden" (ティアーズ・トゥ・ティアラ
外伝) is officially translated by the same Japanese staff to "Tears to Tiara Anecdotes", which is actually a sequel to Tears to Tiara main game.
Phantasy Star Gaiden is a sequel to Phantasy Star 1 (at least, chronological speaking) and, indeed, it is a short story (although it can be discussed the "amusing" part...)
In any case, even if it is an "escort title" doesn't make it less canonic than a "mothership title"... I think.