Both the Tories and Labour have the voting system skewed in their favour.
If you look at the data for the 2010 election you'll see they both get almost the same average amount of votes nationwide per seat they win.
The conservatives won 307 seats with 10,726,614 (36.1%) total votes, which is an average of 34,940 votes per seat won.
Labour won 258 seats with 8,609,527 (29.0%) total votes, which is an average of 33,370 votes per seat won. Sure Labours average is slightly less, but this isn't a significant difference.
Now compare that to the Lib Dems. They only won 57 seats with 6,836,824 (23.0%) total votes, which is an average of 119,944 votes per seat won. That's over three times higher than both the Conservatives and Labour.
It's gets worse with many of the smaller parties too. UKIP got nearly a million votes yet didn't manage to win a single seat in 2010.
Now if it was a "a fair election" (I'll assume by that you mean a proportional system, after all there would be no need for any of the dreaded boundaries that can favour one party over another), then the results would have been quite different.
The conservatives would have won less seats, with 235. Labour would also have won less seats, with 189. However the difference between the two becomes smaller.
Now the Lib Dems would have got a staggering 150 seats. Here is the important part, with that many seats they could have formed a majority coalition with either the Conservatives or Labour. Given that the incumbent government gets the first chance of forming a majority coalition, that means we could well have had a Labour and Lib Dem coalition for the last 5 years.
So with polls showing a similar situation developing for May 2015 (and yes polls can be quite accurate even though they're "not the election"), where is this land slide you speak of? It certainly isn't going to happen under the current system, nor a fairer system. Even if under a "fair" system the Tories win the most seats, it's almost certainly not going to be a landslide.