If I understood you correctly, then CoinMarketCap should do what you're looking for. Let's say you want to compare BTC with ETH:
Yeah it's really easy to navigate and get the desired results on CMC because you can compare with other crypto performance as well but from trading perspective you also have to analyse the single coin chart patterns.
CoinMarketCap : Users can view price charts for individual coins or compare the performance of multiple coins over time.
It has been mentioned above so little advice is to read the posts above to avoid writing something that has been already told as it will not contribute anything on your part.But still you have knowledge that what he asked about is good.