Need games with GIANT ROBOTS

If you're into Strategy RPG, go for Super Robot Wars J on GBA (It's Japan Only, but there's a translation patch on the Internet). Actually, most of the Super Robot Wars franchise is great (And Japan Only, as I said, there are some translation patches online), featuring many mecha anime storylines (Super Robot Wars Alpha has Macross, Evangelion, Gunbuster, Gundam, among others)

Also, the Front Mission series is great.

Supreme Commander

Mechwarrior (except MWO, quite a hated game now)

Oh and Heavy Gear

M.A.V.

Mechwarrior 4 + Mercenaries are free. The same goes for Mechcommander 1+2

"Metal fatigue" - you gota do some patching to make it work on new operating systems. RTS building giant robots (combots) with diferent parts, 3 races for each separate campaings ... good old times :) i think you can download it for free since its an abandonware now.

Transformers fall of cyberton is pretty cool.

One word, my friend: Hawken. Not sure if it's the best ever(probably not), but it is the most convenient: on Steam and free2play(also not with an annoying, crass pay2win system)

If you don't have anything against turn-based combat, Front Mission series is for you. The series makes a strong emphasis on mech customisation, which is a must for a mecha game - you can spend more time in hangar than on battlefield. The games have strong plots and big casts of characters.

Front Mission 1 was released close to the end of SNES lifespan, so it has top notch 2d graphics (I liked it more than low-poly 3d of ps1 era). FM3 has an official English translation and it is also highly recommended. Newer games from the series were released on PS2 and are hard/impossible to emulate.