[UPDATED 01/12/21] Whatever glitch or error was made that caused the game to reappear has apparently been fixed. The links are no longer active. Thanks to Wakayama_PT for pointing it out.
ORIGINAL POST [01/08/21]
Is Activision bringing last gen’s re-releases of Marvel: Ultimate Alliance back on sale or is this a happy accident? It’s hard to know for sure but right now Ultimate Alliance 2 for PlayStation 4 can be found via web search or direct URL on the PlayStation Store across Australian and European territories. Some of the major regions are linked below. No luck so far for North America, Asia, or Japan.
Marvel: Ultimate Alliance 2 (PS4)
Unfortunately, this seems like a temporary reprieve at best. Nintendo and Team Ninja are behind Marvel Ultimate Alliance 3: The Black Order on Nintendo Switch, and it seems particularly suspect that only the second entry has reappeared, and without its Xbox One or Steam counterparts. I haven’t been able to confirm if it’s possible to buy and download the game but I wanted to spread the word for those willing to try. Grab it if you can, while you can, and let us know. Thanks to @CapnSlash for pointing out the news.