Shares of Carnival Corp (CCL) - Get Carnival Corporation Report are on the move Tuesday, rallying 2.4% to $67.66. The stock is just below its 52-week high of $69.89, as investors optimistically bid up the share price.

Helping power the move higher is an upgrade from the analysts at Credit Suisse, TheStreet's Jim Cramer said on CNBC's "Mad Dash" segment.

The analyst, Tim Ramskill, upgraded Carnival to outperform from neutral and bumped his price target to $78.10 from $72.40. His new target implies almost 12% upside from current levels -- even after Tuesday's rally.

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While Cramer agrees on the bullishness of Carnival, he doesn't necessarily agree with the analyst's reasoning behind the upgrade. Ramskill contends that he's no longer cautious on Carnival following its 33% underperformance of the lodging sector since September.

However, being bullish on Carnival because it's underperformed a similar sector isn't a good reason, Cramer argues. "We want to buy stocks because the companies are good," he says.

Why should investors avoid the relative, "if they like this, then they should like that" thesis? Because after going tit-for-tat, one group will eventually falter, explained Cramer, who also manages the Action Alerts PLUS charitable trust portfolio.

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Rather than Carnival or other cruise stocks, like Royal Caribbean (RCL) - Get Royal Caribbean Cruises Ltd. Report or Norwegian Cruise Line (NCLH) - Get Norwegian Cruise Line Holdings Ltd. Report , being attractive because they're cheaper than the lodging sector, they'll be less attractive once the lodging sector suffers a pullback because they're more expensive.

So where does that leave him on Carnival? Cramer says he likes the company because it's well run, undervalued and has solid booking trends. But he's not bullish on it simply because it's underperformed another sector. To be fair, Ramskill also highlighted Carnival's booking "resilience," as well as its earnings momentum as reasons to bet on the stock. 

Investors shouldn't be investing based on industry or sector comparables. "We want people to buy stocks because the companies themselves are inexpensive and undervalued in the stock market. We don't want to buy a company because it's cheaper than another company," Cramer concluded.

Carnival Corp closed at $67.63 Tuesday, up 2.4%. 

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At the time of publication, Cramer's Action Alerts PLUS had no position in any security mentioned.