I am not a philosophical idealist, by which I mean that I do not believe that the only reality is mind/consciousness. But if the only alternative to idealism was materialism (the view that nothing exists but matter) then idealism wins hands down. It's a no-brainer! (Excuse the pun.)
After all, doubting the reality of consciousness is as close to impossible as anything gets. Of course, there are hard-core materialists that try very hard to do precisely this, but don't hold your breath! Success is as far from them as it ever has been and as far as it ever will be. Doubting the reality of matter, however, is a different kettle of fish. That is indeed possible. After all, we only have access to it via the mediation of consciousness.
Idealism can be imagined to be true (even if it is false) but while I suppose that one can possibly make sense of the claim "materialism is a possible state of affairs in an alternative universe," I am at a loss to understand how anyone can even imagine that believing "materialism is the truth about our world" is even possible. The very imagining of its truth is inexplicable in purely materialist terms and so if one can imagine that the proposition is true then the proposition must be false. Or so it seems to me.