This is obviously a silly comparison on many levels, but I'll give a semi-serious answer. First of all, if you're going to compare Oliver Cromwell to anyone, I'd suggest Napoleon. Like Cromwell, he was a military strongman who took power after a bloody revolution against monarchy. In that comparison, as in this one, I'd choose Cromwell, for the simple reason that he killed way less people. Hitler and Napoleon were bloodthirsty conquerors whose warring led to the deaths of millions upon millions - yes, Napoleon may still have been preferable to the reactionary coalitions assembled against him, but that doesn't excuse his imperialist warmongering - while Cromwell was nothing of the sort.
Cromwell's foreign policy was a sound one, aimed at shoring up his regime at home and promoting the republican interest abroad. He was not a dogmatic Protestant fanatic as has often been portrayed, but a pragmatic politician willing and able to work within the framework of the post-Westphalian European state system. In the First Anglo-Dutch War, Cromwell fought against fellow Calvinists in the Netherlands, whom he opposed on ideological grounds.* A few years later, he formed an alliance with Louis XIV - yes, that Louis XIV. Cromwell also granted a degree of religious toleration to Protestant dissenters, disestablished the state Church of England, and allowed the Jews to return to England for the first time in nearly 400 years.
And now we reach the great dark spot on Cromwell's resume, the destruction of Ireland. It was indeed horrific and inexcusable, and history has judged him for it. But given the time he lived in, such actions were sadly all too commonplace. If Cromwell committed genocide in Ireland, then so too did the Catholic Imperial armies that sacked Magdeburg, forcibly re-Catholicized Bohemia, and terrorized Protestants throughout the Holy Roman Empire. The 17th century was a bloody time, and by those standards Cromwell was not exceptionally bloody.
Finally, as I know there are many Jefferson fanboys and Hamilton haters on this forum, I'd like to note that Jefferson (and Adams) held Cromwell in high regard, while Hamilton dismissed him as a demagogue. Liberals and republicans in the Anglosphere owe much to colonel Cromwell and his boys in the New Model Army, whatever one thinks of the man.
*The Commonwealth of England was a republican regime stoutly committed to the overthrow of monarchy, while the Netherlands - though a republic - had a strong Orangist faction which sought to restore the hereditary Prince of Orange to the Stadholderate. The House of Orange was dynastically linked to that of Stuart, meaning that a monarchy in the Netherlands would not only subject the Dutch people to despotism, but also threaten the security of the Commonwealth. In the treaty that ended the war, the English included a secret provision called the Act of Seclusion, which prohibited the young Prince of Orange from ever becoming Stadholder. How ironic that the same William of Orange would go on to become the great Protestant savior of England! The Glorious Revolution was very much not a victory for the more radical Cromwellian republicans, many of whom afterward became Jacobites (Protestantism and Patriotism: Ideologies and the Making of English Foreign Policy, 1650–1668, Steven Pincus). 
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