I think closer to the latter. Starting a simulated person, running them for a while, and then ending and discarding the resulting state effectively murders the person. If you then start another copy of that person, then depending on how you think about identity, that goes two ways:

Option A: The new person, being a separate running copy, is unrelated to the first person identity-wise, and therefore the act of starting the second person does not change the moral status of ending the first. Result: Infinite series of murders.

Option B: The new person, since they are running identically to the old person, is therefore actually the same person identity-wise. Thus, you could in a sense un-murder them by letting the simulation continue to run after the reset point. If you do the reset again, however, you're just recreating the original murder as it was. Result: Single murder.

Neither way is a desirable immortal life, which I think is a more useful way to look at it then "happy".