See I disagree. I think at heart Jimmy is a good guy. Chuck puts on a front of being a good guy but he's really an ass and thinks he's better than everyone.
I'm not really talking about personality though. I'm talking professionally. We all know Jimmy ends up representing drug dealers, losers, con men, etc. He was one himself and never shied away from still being one, even when he was working as a lawyer. Yeah, he put up the front that he was doing for the people getting ripped off by Sandpiper, but in reality, he loves the con game. They even had that episode in season 2 where he was bringing Kim in on it. I'm not doubting he can be personally a nice guy, but most of his tactics are below board, even when doing the right thing.
Yeah, Chuck is an ass. He'd definitely be that guy who would keep you from inviting your friends to the country club. But, he believes in the law and he believes it's sacred. He would use the law to get his verdict, not twist the law and use bad tactics to get his way. And he doesn't like Jimmy skirting those laws to get his verdict. If Jimmy hadn't proven to be the ultimate con man his entire life, I don't think Chuck would be the way he is. Chuck obviously does suffer from, "I've done it right my whole life, why does everyone like Jimmy so much more?" syndrome though.
This is how I see the first two seasons. Now, I can see how it can be perceived both ways, but so far, what I've seen gives me the opinion that if it weren't for Chuck, Jimmy wouldn't be a lawyer. He's always been trying to impress his older brother. That's the only reason he follows any laws at all. Yeah, I can see how some people see Chuck being overbearing might cause Jimmy to do the bad things he does. Personally though, it seems to me, the only reason that Jimmy does anything good, at least as the law is concerned, is to impress Chuck and get his brothers favor.
In the end, this is probably another nod to the good writing on this show. It can be seen both ways. Is there a right, is there a wrong, I'm not sure, but I'm sure if we sat long enough and hashed it out over a beer, we'd probably both be able to see the others point. As I said already, I certainly can see how Chuck is a source for both good and bad in Jimmy.