How would you compare these companies in terms of how prestigious it
is to have worked there as a software engineer:
Microsoft, Google, Oracle, Goldman Sachs
(Goldman Sachs is a wall street firm, but they hire programmers to
figure out the values of commodities they're buying and selling.)

It is hard to compare, and it would depend on what type of employer
would review your CV.

Companies like Google are extremely well regarded -- but having worked
there as a software engineer could have little impact if you are
looking to find a job developing software for financial backends. On
the other hand, having worked for Microsoft or Oracle would probably
have a positive impact, since it is likely you would have been exposed
to a wider range of technologies, methodologies and work practices.

As a rule, you can probably say that the more specialised the company
is, the less impact it will have in terms of boosting your career. On
the other hand, working in an environment or company where you are
exposed to different technologies and practices is the way to improve
your employability.