First off, since we're discussing rocks, I assume we're talking about the Commander format.
I do agree with each of you.
I tend to tailor my mana rocks to the deck. Expecially those rocks that have CMC 3 or greater. I do play casual Commander, where 3-mana mana rocks are viable and normal to see, but I still feel that for 3 mana, it needs to do a little something extra for me. I have NEVER run
Manalith. I will run a keyrune if I want a sleeping creature. I will run
Darksteel Ingot if I want to guard against it blowing up. I will run a cluestone if I want the card draw. Although for card draw, I will use
Mind Stone first, then
Commander's Sphere, and then probably a locket. (I have not played with the lockets much yet, so my preference for locket over cluestone is only theoretical at this point.) But none of these are auto-includes for me. I am also a fan of
Cultivator's Caravan, just because it's a mana rock that can be thrown at someone later on - for FIVE damage!
The only auto-includes that I have in EVERY deck (regardless of color mix) are:
Sol Ring - no one disputes that this is the king of mana rocks.
Thran Dynamo - I think this one is very underrated. I like it better than
Gilded Lotus, since it costs 1 less, but still makes 3 mana.
Signets & Talisman (non-mono decks) - I do agree that a Talisman is mildly better than a signet. The trick to playing them is using the Talisman for colorless/generic requirements whenever possible to minimize the pain (same concept as properly utilizing painlands).
Fellwar Stone - Especially useful with decks that steal things by letting you pay activation costs outside your color identity.
Thought Vessel - "Reliquary Rock".
Beyond that, like I said, I like to customize the ramp package to the deck. Certainly, if I'm in green, more of my mana ramp will be in the form of dorks and ramp spells.
A tip that I use when I am building is that I use about 10 pieces of mana ramp. I only permit one or two of those pieces to cost more than 3 mana. This is where I slot
Gilded Lotus,
Caged Sun,
Black Market,
Gauntlet of Power,
Gauntlet of Might,
Hedron Archive,
Dreamstone Hedron and such things.
I also like
Solemn Simulacrum as ramp, although I typically count it as a card-draw slot, since he costs 4 mana.
I have also use a host of others, like
Burnished Hart,
Armillary Sphere,
Lotus Petal,
Lotus Bloom, the mana Myr,
Mana Vault,
Mana Crypt,
Basalt Monolith. You just have to be selective about what deck you put them in.
Happy Brewing!