You're trying to compare two different situations.
The Republicans lost the White House.
However...
The Democrats have lost more seats in the House, Senate, State Governors, and State Congressional levels than at any point in their history. To say that the two situations are the same is just not accurate. Obama's "legacy" is responsible for that whether you want to admit it or not.
So, if you're wanting to place your hope in a miraculous Dem comeback in two years then four, I've got some great swampland in Florida to sell you.