The Polish Przypadki are the most beautiful things on earth, despite the difficulties, non-Polish speakers might have in learning this language.
A language that works with a case-system is more rich ,more "intimate" more "close",so to speak, than languages that just make use of prepositions.
Least we forget, English has cases, too! They exist throughout Germanic languages as well as Slavic languages. The cases in the English language were simplified after the Norman invasion of England in 1066. For this same reason, many names in English of cooked animals are different than the names of the living animal - the dead animal names are French because the Normans were the aristocracy and they didn't have to deal with live animals; they only had to deal with the animals on their plates - but I digress.
Cases are not necessary to human syntax. Most Asian languages don't have cases and only a handful of tenses, at the most.
Cases do, however, allow for a kind of subtly that would otherwise not be possible (not in the same way, anyhow). But Polish has TOO MANY friggin' cases! Any language that has more cases than Latin deserves to die because it it too complicated! As I would often joke when at the pub with my friends: "I have to drink more - I'm not drunk enough to speak Polish yet." :D
Icelandic is quite nice... 4 cases (the same 4 that appear in English) regularly used with pretty straight forward grammatical usage rules (not to mention some funny grammar) plus some wicked-awesome vowels! Of all Germanic languages, I think Icelandic is the winner, just as I think Polish, despite its case system, is the winner for Slavic languages.
Enough of this rant. Have a good night/mornings wherever you are.