Is there a source that lists all SCOTUS decisions for, say, the past 25 years, which names justices in the majority, versus dissenting justices (even better, separated by written opinion so that separate opinions "on the same side" can be found)? Something quicker than me reading every decision.
The Supreme Court database (release 2019-01 onward) maintained by Washington University in St. Louis not only allows one to download a vast amount of coded data about SCOTUS decisions, it also allows one to do exactly the sort of analysis that is described in the question and to do it using online tools.
The version of the database that was available at the time the question was posted did not have the easy user-interface that is now available.
Yes, CourtListener has several such graphs charting liberal vs conservative Supreme Court decisions