In multy-party system, you often end up voting for a party that then on your behalf makes deals with other parties to form coalition, deals you did not agree upon. It is like delegation of duty, or rather usurpation of your vote. And you still end up with fucked up government that does not reflect your values. In two party system you are the one who are forced to make those compromises.

In multiparty system, often one coalition (or even party) dominates for many years and election cycles. The two party system nearly guarantees strong opposition.

I still think that two party system is better.