Would you think china was more democratic if the 8 parties had a larger share of the votes

Yes, broader representation would literally be more democratic.

Why would a larger share be better?

Because that's how democracy works.

Is democracy a function of how many parties are in government?

Democracy is a function of broad representation in government, ideally complete representation, though this is difficult to achieve in practice.

Would it be a good thing if the president had a minority share of the vote?

In the PRC, only local officials are elected, and only candidates which are approved by the ruling party can be nominated for those elections. The president is not subject to direct popular election.

Under the Constitution of the People's Republic of China, the CCP is guaranteed a leadership role, and the National People's Congress therefore does not serve as a forum of debate between government and opposition parties as is the case with Western parliaments.[9] At the same time, the Constitution makes the Party subordinate to laws passed by the National People's Congress, and the NPC has been the forum for debates and conflict resolution between different interest groups. The CCP maintains control over the NPC by controlling delegate selection, maintaining control over the legislative agenda, and controlling the constitutional amendment process.[9]

ref

The ruling party controls delegate selection, the legislative agenda, and constitutional amendments, which ensures that they can maintain their own control indefinitely. This is the opposite of democratic.