Depends on what point of view you are going by, from a webmasters point of view google is very good, you can earn money via adsense, sell products via adwords and rank well in there search results, so good invention for webmasters. But we are just the minority trying to do these things, so overall from a normal internet users perception I could live tommorow without google easily, and would not class them as anything special, playing chess online or poker with someone in a different country than I am is a million times better than what google offer me, talking and sharing music on msn is a million times better than anything google currently offer me, as this continues with loads of other sites and applications, so no google as an internet user is handy and my #1 search provider, other than this I would not miss them if they were not here tommorow.
It helped worldwide communications expand, so it's certainly influential. Best ever though? Can't say that.
Why should it be the best internet invention? Their mainproduct, the searchmchine, is better than the competitors are. But they are all working with more or less the same methods. So there is nothing revolutionary abot it. just my opinion.
At the moment, you can say that it is. But may be in the future, we will see something much more better