The games I know of that feature Wesker are:
Resident Evil Zero
Resident Evil (all versions)
Resident Evil Code: Veronica (all versions)
Resident Evil 4 (all versions)
Resident Evil: Umbrella Chronicles
Resident Evil 5
The only games he does not physically appaear in (but still appears in one photo in the RPD and is mentioned in several files) are 2 and 3, but when those games were made everyone still thought he was dead.
So that's a total of six games, not including remakes and re-releases, which would overall increase the count to around fifteen. Chris places second physically appearing in four (five if you include the Battle Game in Resident Evil 2).
.