If you're talking about Democrats and Republicans, I think you'll find they're both decidedly right wing compared to political parties elsewhere in the world.
That is a common misconception. If you look at actual policies the US is pretty far left in many ways. I spent a few days studying this a year or two ago, and the US is to the right of about 3/4 of Western countries, and to the left of about 1/4 of them.
Looking at that, there's hardly anything between Obama and Romney.
I am familiar with the website from which that chart comes, and I don't consider it credible. How does it decide where to put the center? It is arbitrary.
I use a non-arbitrary definition: the status quo is center. Anyone who wants modernize authority is a leftist, anyone who wants to diversify authority is a rightist. Anyone who is more of a leftist than Marx is far left, anyone who is more of a rightist than Confucius (the man himself, not his disciples) is far right.
You are correct that Obama and Romney seem to fall pretty close to each other on a left-right spectrum, but the truth is that they are on the left. This is because they both want to move the status quo to the left. That is indisputable. We know that Obama's policies are far left because of his actions on the lumpenprole (people that Marx did not care about). Romney could have gone pretty far left when he was governor of Massachusetts, but he didn't. So we can conclude that he (like most Mormons) is only a center leftist.
As for it being "nice" to see UKIP do well, I'll have to disagree. Scapegoating minorities and blaming them for all your economic problems is the kind of backwards thinking that we, as a species, should have been able to move past by now. That sort of BS should have ended with WW2. UKIP are disgusting, vile creatures.
None of the top three parties addresses any of the concerns of the average person. UKIP not only addresses them, but has decent solutions. Also "move past by now"? Do you see the demographic shifts that are happening around you? How many children does the average Labour supporter have? How many does the average UKIP have? I'm guessing that the latter is at least twice the former. In the US it will only be a couple of generations before we shed the progressives. They'll be a few of inconsequential weirdos instead of the ruling class.