I pulled the lyrics from the Hey Hey 16K web site - having the original punctuation and layout sometimes help us understand the intent better:
It made a generation who can code
A bubble before proper consoles, who all know
That the games you get today, may be very flash
But there'll (sic) never beat the thrill
Of getting through Jetpac
At the bottom of the page the author of the lyrics writes
... it often seems to me that my adolescence in the 1980's is being wiped out of history...
So I think the definition of the noun "bubble" by Oxford Living Dictionaries of "Used to refer to a good or fortunate situation that is isolated from reality or unlikely to last." fits the best.
I would interpret the lyric to mean there was a short "golden age" before "proper consoles" came along when hobbyists produced really innovative games, but it ended rather abruptly.
It might be related to the Video game crash of 1983 as Mobeer mentioned in a comment. "Bubble" can also be used to refer to a period of very fast financial growth that collapses (a "financial" bubble). I'm not sure about this though, because the song mentions "Commodore 64" which survived the crash and "and went on to become one of the best selling computers of all time."