Odd comparison, odd being for the reason that I cannot find ANY similarity beyond the simple fact that they both were put together without Freddie's active input at least in the main production cycle. One slight comparison I see is how along with A Day at the Races they start or early on contain a music that reprises at the end via a slight return.
Made Im Heaven was theme to Freddie's tragedy. It contained a very softer than usual bulk of ballads and light tunes with only moments of really rocking out, at least to Queen's reputation. The album is all about one final run of tunes led by Freddie with the classic 4 piece unit overall.
Cosmos Rocks has the space theme but is loaded with blues tunes and rockers, ballads being little more than a few slower songs with mostly a blues flavor rather than ballad like softer sounds. Lyrically it's an all-time low.
The biggest difference I see is how everyone critics and fans alike were destined to accept MIH for the sake of Freddie being one album away from exiting his great legacy. While that was impossible to bash, Cosmos Rocks seems impossible to accept for critics and cynical fans being that -Deacon and years of time off added, Brian and Roger use the name for a project that utilizes a singer, great or not, a singer who is not Mercury.
Also MIH is for more than post-humous reasons the most production created album as any or more even than all the other Queen releases. Cosmos Rocks seems clearly to me to be raw more so than all but one, Queen's debut record which only plays with less studio control due to it's low budget/short time frame limitations.
I rate MIH as a better album, but the better half of each is a closer call.