I have to say that I find games companies particularly slow-witted with regards to their back-catalogues.
Consider a re-released SH3 with nothing extra other than up-to-date graphics and support for wide-screen (or even multiple screens), that would still function with mods and existing saved games. Would I pay to upgrade? - yes ( even with knowing that there are mods out there to do that already). More of the same, but a little better, as it were.
The same applies to the original CoD UO - a simple update to more modern graphics would be good... and probably a large number of still-played older games could support that model. Much better than micro-transactions.
Still, what do I know.