During the middle ages, was the beer they drank back then comparable to modern day beer in terms of taste?

Like most answers, it depends on when you're asking about and what kind of beer. A short answer is no. A modern mass produced lager beer like Budweiser would almost be a completely different beverage compared a beer brewed in 1300, but some authentic English ale would be closer, but still not the same.

First of all, the main ingredient in beer, malted barley, was quite different in the middle ages compared to today. Barley has to be malted to convert the starch in the seed to usable sugar, which involves wetting the barley, letting it sprout, then heating it up to stop the enzymes and the seed from growing too much. With modern technology, the malting process can be very precisely controlled, allowing a very light malt, to very dark malts (this what creates the difference in colour and taste between say a pale ale and Guinness). However, the only way to do this back in the middle ages was of course, over a fire, which was harder to control, resulting in generally darker beer than today, and the smoke from the fire smokes the barley and this imparts a smoky flavour to the beer (if you've ever had a smoky Scottish whisky, it's the same thing). So to start with, your beer is going to be smokier and darker than (almost) all beers today (and this is all without going into the "adjuncts" commercial breweries add such as corn and rice to get lighter, cheaper beer).

Hops, the other main flavour and aromatic components in beer and gives it bitterness (and also helps to stop spoilage), was first used in beer around 1400. Before that beers were flavoured with local herbs and flowers and so, while I've never seen a recipe/description from this time, I would imagine a beer would change quite dramatically between regions depending on what local flora is available. It might be weird to think, but the addition of hops to beer was a controversial topic and a lot of British ales until around the 1700s refused to use hops and believed that a real beer did not use hops. So without hops, a beer would taste much more sweeter because of the lack of bitterness to balance out the sweet.

The third, and maybe most important development in creating a modern beer was the discovery of lagering in Pilzen (hence pilsner) in the now Czech Republic in the early 1800. Beers can be either ales or lagers. An ale is is quickly fermented at a higher temperature (around 20c) for around 5 or so days with yeast that floats on the top of the tank. This creates a more darker, stronger flavoured beer. Lagers on the other hand ferment much slower at a lower temperature (usually about 10c for a month or more) with yeast that sinks to the bottom of the tank. This was traditionally done in cool caves, hence the name, which is German for cave. This slow ferment makes the beer a lot lighter in colour and taste, which became very popular, and led to our modern light lagers.

Finally, before the modern industrial age, all beer would have been fermented and stored in wooden casks, at cellar temperature, ~12 to 14c, and the only carbonation would have be from the residual CO2 left from the fermentation, creating to a modern palate, a warm, flat beer. If you've ever had a traditional English ale from a handpull, that's it. Beers also would spoil quite easily, within a month or so, and would be likely to vary between batches, thus you would likely only be able to drink the beer from your local town's brewery. With the advent of modern refrigeration, storage and packaging, forced carbonation, and germ theory, breweries became more and more consistent between batches, stopped their beer spoiling so easily, and created the modern beer we know today. It's interesting to note that breweries like Budweiser became dominant not because they were nessarially good beers, but made a consistent product that spoiled less and could be transported further.

So to sum up, a beer in the middle ages would have been a warm, flat, slight smoky, sweet alcoholic beverage that tasted like the local herbs of whatever village you lived in. Still better than drinking likely contaminated water.

I can provide sources/further reading if anyone is interested.