oversized yugioh cards YU-GI-OH! - Big Eye (LCYW-EN230) - Legendary Collection 3: Yugi's World - 1st Edition Junk Giant | Card Details

For Pokemon, the fan-made site Pokecollector comes highly recommended, whilst Yu-Gi-Oh

Pikachu Pokemon My First Battle Keep track of your collection value over time

Maze's End, I think, is a no-brainer

I was looking through the cards and I noticed something odd: the Diglett, Dugtrio and Sandshrew don't have resistance to lightning, despite this resistance being a staple for ground-types

There is the official Pokmon Trading Card Database, which will help you spot any text or stat differences, but isn't great for differentiating colors (since your monitor may not precisely match the colors a printed card would appear in your room), and of course it can't help you with determining the feel of the card