While they do both share simmilar qualities; obsessive nature, the WHY in every reason, and the same philosophy: Everybody Lies, they are both their own person.
House is a drug addict and only cares about himself (SOMETIMES other people), and he hates/picks apart every quality he can find in a person to figure out who they really are.
Cal, on the other hand, cares about almost everyone and the only problem he has with people is the fact that he can't hold a relationship with anyone because of his science and he notices every single negative in a person, but ignores the positives.

So yes, they are very close in personality, and yes, they DO belong together (maybe a House MD / Lie to Me* crossover episode one day), but they are their own person, and in this case, their own character.

As JH said, they are their own person/character.

House doesn't have the possibility that Cal has to actually BE in a stable relationship with someone. Even though Cal's possibility is small, it's so much more probable that he will be with someone in the end while House I'm afraid to say will most likely end up alone.
Just adding that to JH's list.

They both have insane methods of doing their jobs. . . :)

the only difference I can see if that House puts a barrier and blocks everyone who loves and cares for him out while Cal kind of welcomes them in.... kinda and House "likes" being miserable and Cal not so much lol

Aw JH I think you're a bit harsh to House.
I think they're similar in their desire for the truth and the rational way in which their minds work and how sometimes they can be quite blunt.

But there are significant differences. House is a rather miserable character who shuts himself off to everyone, even the people he's close to. While Cal tends to be quite honest with those he's close to, Gillian he has to be honest with because she could tell otherwise ;)

Another significant difference is that Cal knows when to shut off his powers of deduction about how people are feeling, House persues everything he finds out.

I agree with pretty much all Juliana_House said - pretty much, Lightman is a bit more human than House... though both will stop at nothing to get at the truth, Lightman is more gentle.
However, they are both fantastic characters to watch... plus they both have strange/ abnormal walks!

I'm absolutel agree with you all, Lightman and House do have some things in common and sometimes they are completely different from each other. And offcourse I love both guys and both show. :-)