N64 is probably the easiest one since it was actually popular even with mistakes made.
Give it a CD-ROM drive and a cheapo 4MB RAM "loading pool" (to mitigate load times), launch at $249.99 instead (this was supposed to be the original price anyway), and drop to $199.99 in 1997 (they cut to $149.99 by March 1997 in a rush anyway ... it's like you might as well just have added the damn CD drive then anyway).
Have a meeting with Squaresoft circa 1995/1996 to say "hey look, if you want to put FF7 on Playstation, fine, but at least give us a port, we've compromised and we have a CD format too and will have games from everyone else now including Dragon Quest 7, you're just going to lose a lot of money by ignoring us, we'll even give you a stack of money too and we'll pay for the port".
System launches in summer/fall 1996 with Super Mario 64, Resident Evil 1 port, Street Fighter Alpha 2, Pilotwings 64, Madden NFL '97, NHL '97, and a port of Tekken 2 soon after. Castlevania: SOTN in the early months of the system too. See how that immediately looks much better? Games are also much cheaper now that they're on the disc format.
Oh and I'd also buy the rights to the James Bond movie license prior to GoldenEye 007's release either indefinitely or for a further 10 years.