I went to the CNN website and tallied up all the House district votes. There were 58 districts where one party or the other did not run a candidate and CNN just left those blank. I think in 44 of those districts there was no Republican candidate and in 14, no Democratic candidate. Also, CNN doesn't include any third party candidate.
Of course, the returns aren't final or official anywhere and there are probably still several million votes to be counted, so this is strictly preliminary.
So, anyway, these are the totals for the 377 districts.
101,895,633
Democrats 54,598,746 53.6%
Republican 47,296,887 46.4%
If we adjust for the candidate unopposed, who in every state but Florida is still on the ballot and still gets votes, by say giving them 150,000 votes each, we can readjust the preliminary figures for a more accurate total.
Democrats: 44 unopposed canidates * 150,000 = 6,600,000
Republicans: 14 unopposed candidates * 150,000 = 2,100,000
Democrats: 54,598,746 + 6,600,000 = 61,498,746 55.3%
Republicans 47,296,887 + 2,100,000 = 49,396,887 44.7%
I'd say that's approaching a landslide win.