That'd be an apples and oranges comparison. W's errors helped lead to the deaths and maimings of 10,000ish American Soldiers or the entirely needless suffering in New Orleans after Katrina hit and unforgivable federal delay.
Obama's mistake is not much more than a little egg on the face. It is important to keep perspective here.
How many mistakes did Bush fess up to? Any at all? Ignoring the terror threat prior to 9/11, the woefully run Iraq occupation, disaster relief, etc... serious mistakes that led to serious consequences.
Obama admitted error is certainly a nice change of pace. Yes, it'd be nice if Obama was perfect, but he isn't, nor can he be, so why string him up because he isn't?
It is amazing, Obama has been in the job for less than a month and already people are ready to kick him out. Complaining about nominees with tax issues when the US military base in Kyrgyzstan is in limbo (which directly affects our actions in Afghanistan and is a result of Russian pressure on Kyrgyzstan) and the Obama Admin's reaction and resolution to that are the big fish, not the tax issues of nominees. That is how you decide the leadership of person, the important stuff, not the little stuff.
One guy made an error that involved payroll taxes that was actually followed through when he paid someone to do his taxes. Another nominee had about $1000 in back taxes. Those aren't huge mistakes. They certainly are errors, but anyone that has to do their taxes as a self-employed contractor will know how unbelievably difficult they can become.
Tom Daschle, I'm rather glad to see him go even without his glaring $100+k tax error. While he seemed to be everyone's pick for the Health Care reform, he seemed to be too in with the Health Care industry.
The reason why the tax code is so complicated is so that the rich can avoid it.