This question tries to  assess your engagement level in your current job-profile i.e., how well have  you evaluated all the aspects involved in your profile. The interviewer(s) seek  to know how do you judge your own performance. 
This is a tricky question  to answer. You need to be diplomatic while answering this.
Following are some  alert points embedded in this question:
  1. Tell them about how  well the job profile suited you and what made you choose that profile in the  first place.
  2. Speak about your recognition and rewards that  you earned while working in that job.
  3. Remember that there always is a room for  improvement in a job, irrespective of it being a clerical level job or a senior  level job. Hence, DON’T let your answer to this question to be a straight ‘no’.  This will make you sound arrogant and over-confident.
  4. There is no harm  in accepting your mistakes or shortcomings; what is more required is your urge  to correct them and improve. Hence, tell them if you identified any such scope  of improvement in your last job. However, support your answer by stating how  you wish to incorporate the improvement in yourself. 

Now, it’s time for 'participation':
*Assume that you are sitting in the interview room now.
*You have been asked to ‘Do you think that you could have done better in your last job’. Go ahead; give it a try on how to answer the same. Post your own answers and get them reviewed .

Do you think that you could have done better in your last job?