Yeah good points.
Mega Drive/Genesis (40 million sold), Playstation One (100 million), Playstation 2 (150 million sold), Nintendo DS (150 million sold) are "mid-gen" cycles by these definitions.
Genesis came out in '89, just three years after the Sega Master System.
Playstation launched at this point in the SNES life cycle (1994 in Japan, 1995 in North America).
PS2 launched a year ahead of its competitors.
XBox 360 launched a year ahead of the Wii and PS3.
DS replaced the GBA after only 3 1/2 years.
they're not good points. launching a year ahead of the competition is not "mid-gen" WTF
In that case, Dreamcast isn't a "mid-gen" console either then.
The only examples of mid-gen system releases would the DS and Sega Genesis, and both were hugely successful and they represent the best selling Nintendo and Sega systems respectively.
Really though all this stupid, there's no singular "formula" for a successful console. You execute properly or you don't.
Even the Dreamcast, had Sega not be on wonky financial footing may have very well outsold the GameCube or XBox at least, if Sega simply had the money to stay in the race.