A lot (unanimous?) of hate for Google Shopping in here. I actually think it's great. Amazon no longer has the lowest price on all kinds of different goods. So I use Google Shopping tab to price-compare across every possible retailer for, say, a specific rain jacket or a TV. There is some junk but if you mentally filter for online retailers you trust/have heard of, you can get a great deal compared to just running to Amazon sometimes. And the filters/search works reasonably well.

That depends heavily on where you are located. Here in Germany we have excellent shopping search engines with Geizhals and Idealo.

Particularly Geizhals is an indispensable product research tool since it does a great job of collecting, normalizing and filtering product attributes - it replaces the tedious process of comparing several incomplete spec sheets with different terms, values and units.

Unfortunately there don't really appear to be many good alternatives.

https://pricesearcher.com seems to be a fairly featureful replacement for Pre-2012 Google Shopping/Product Search/Froogle, but it's UK only and I'm not sure about its long-term survival prospects (and it doesn't include eBay listings).